Communication apparatus and communication method

ABSTRACT

The purpose of the present invention is to inhibit an increase in the amount of A/N resources, without changing the timing at which the error detection result of an SCell is notified when UL-DL configurations to be configured for each of the unit bands are different, from the timing at which the error detection result is notified when just a single unit band is configured. A control unit transmits, using a first unit band, a response signal including error detection results about data received with both the first unit band and a second unit band. In a first composition pattern set for the first unit band, an uplink communication subframe is set to be the same timing as at least an uplink communication subframe of a second composition pattern set for the second unit band.

TECHNICAL FIELD

The present invention relates to a terminal apparatus and a transmissionmethod.

BACKGROUND ART

3GPP LTE employs Orthogonal Frequency Division Multiple Access (OFDMA)as a downlink communication scheme. In radio communication systems towhich 3GPP LTE is applied, base stations transmit synchronizationsignals (i.e., Synchronization Channel: SCH) and broadcast signals(i.e., Broadcast Channel: BCH) using predetermined communicationresources. Meanwhile, each terminal finds an SCH first and therebyensures synchronization with the base station. Subsequently, theterminal reads BCH information to acquire base station-specificparameters (e.g., frequency bandwidth) (see, Non-Patent Literatures(hereinafter, abbreviated as NPL) 1, 2 and 3).

In addition, upon completion of the acquisition of the basestation-specific parameters, each terminal sends a connection request tothe base station to thereby establish a communication link with the basestation. The base station transmits control information via PhysicalDownlink Control CHannel (PDCCH) as appropriate to the terminal withwhich a communication link has been established via a downlink controlchannel or the like.

The terminal performs “blind-determination” on each of a plurality ofpieces of control information included in the received PDCCH signal(i.e., Downlink (DL) Assignment Control Information: also referred to asDownlink Control Information (DCI)). To put it more specifically, eachpiece of the control information includes a Cyclic Redundancy Check(CRC) part and the base station masks this CRC part using the terminalID of the transmission target terminal. Accordingly, until the terminaldemasks the CRC part of the received piece of control information withits own terminal ID, the terminal cannot determine whether or not thepiece of control information is intended for the terminal. In thisblind-determination, if the result of demasking the CRC part reportsthat the CRC operation is OK, the piece of control information isdetermined as being intended for the terminal.

Moreover, in 3GPP LTE, Automatic Repeat Request (ARQ) is applied todownlink data to terminals from a base station. To put it morespecifically, each terminal feeds back a response signal indicating theresult of error detection on the downlink data to the base station. Eachterminal performs a CRC on the downlink data and feeds backAcknowledgment (ACK) when CRC=OK (no error) or Negative Acknowledgment(NACK) when CRC=Not OK (error) to the base station as a response signal.An uplink control channel such as Physical Uplink Control Channel(PUCCH) is used to feed back the response signals (i.e., ACK/NACKsignals (hereinafter, may be referred to as “A/N,” simply)).

The control information to be transmitted from a base station hereinincludes resource assignment information including information onresources assigned to the terminal by the base station. As describedabove, PDCCH is used to transmit this control information. This PDCCHincludes one or more L1/L2 control channels (L1/L2 CCH). Each L1/L2 CCHconsists of one or more Control Channel Elements (CCE). To put it morespecifically, a CCE is the basic unit used to map the controlinformation to PDCCH. Moreover, when a single L1/L2 CCH consists of aplurality of CCEs (2, 4 or 8), a plurality of contiguous CCEs startingfrom a CCE having an even index are assigned to the L1/L2 CCH. The basestation assigns the L1/L2 CCH to the resource assignment target terminalin accordance with the number of CCEs required for indicating thecontrol information to the resource assignment target terminal. The basestation maps the control information to physical resources correspondingto the CCEs of the L1/L2 CCH and transmits the mapped controlinformation.

In addition, CCEs are associated with component resources of PUCCH(hereinafter, may be referred to as “PUCCH resource”) in a one-to-onecorrespondence. Accordingly, a terminal that has received an L1/L2 CCHidentifies the component resources of PUCCH that correspond to the CCEsforming the L1/L2 CCH and transmits a response signal to the basestation using the identified resources. However, when the L1/L2 CCHoccupies a plurality of contiguous CCEs, the terminal transmits theresponse signal to the base station using a PUCCH component resourcecorresponding to a CCE having a smallest index among the plurality ofPUCCH component resources respectively corresponding to the plurality ofCCEs (i.e., PUCCH component resource associated with a CCE having aneven numbered CCE index). In this manner, the downlink communicationresources are efficiently used.

As illustrated in FIG. 1, a plurality of response signals transmittedfrom a plurality of terminals are spread using a Zero Auto-correlation(ZAC) sequence having the characteristic of zero autocorrelation intime-domain, a Walsh sequence and a discrete Fourier transform (DFT)sequence, and are code-multiplexed in a PUCCH. In FIG. 1, (W₀, W₁, W₂,W₃) represent a length-4 Walsh sequence and (F₀, F₁, F₂) represent alength-3 DFT sequence. As illustrated in FIG. 1, ACK or NACK responsesignals are primary-spread over frequency components corresponding to 1SC-FDMA symbol by a ZAC sequence (length-12) in frequency-domain. To putit more specifically, the length-12 ZAC sequence is multiplied by aresponse signal component represented by a complex number. Subsequently,the ZAC sequence serving as the response signals and reference signalsafter the primary-spread is secondary-spread in association with each ofa Walsh sequence (length-4: W₀-W₃ (may be referred to as Walsh CodeSequence)) and a DFT sequence (length-3: F₀-F₂). To put it morespecifically, each component of the signals of length-12 (i.e., responsesignals after primary-spread or ZAC sequence serving as referencesignals (i.e., Reference Signal Sequence) is multiplied by eachcomponent of an orthogonal code sequence (i.e., orthogonal sequence:Walsh sequence or DFT sequence). Moreover, the secondary-spread signalsare transformed into signals of length-12 in the time-domain by inversefast Fourier transform (IFFT). A CP is added to each signal obtained byIFFT processing, and the signals of one slot consisting of seven SC-FDMAsymbols are thus formed.

The response signals from different terminals are spread using ZACsequences each corresponding to a different cyclic shift value (i.e.,index) or orthogonal code sequences each corresponding to a differentsequence number (i.e., orthogonal cover index (OC index)). An orthogonalcode sequence is a combination of a Walsh sequence and a DFT sequence.In addition, an orthogonal code sequence is referred to as a block-wisespreading code in some cases. Thus, base stations can demultiplex thecode-multiplexed plurality of response signals using the related artdespreading and correlation processing (see, NPL 4).

However, it is not necessarily true that each terminal succeeds inreceiving downlink assignment control signals because the terminalperforms blind-determination in each subframe to find downlinkassignment control signals intended for the terminal. When the terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminal wouldnot even know whether or not there is downlink data intended for theterminal on the downlink component carrier. Accordingly, when a terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminalgenerates no response signals for the downlink data on the downlinkcomponent carrier. This error case is defined as discontinuoustransmission of ACK/NACK signals (DTX of response signals) in the sensethat the terminal transmits no response signals.

In 3GPP LTE systems (may be referred to as “LTE system,” hereinafter),base stations assign resources to uplink data and downlink data,independently. For this reason, in the 3GPP LTE system, terminals (i.e.,terminals compliant with LTE system (hereinafter, referred to as “LTEterminal”)) encounter a situation where the terminals need to transmituplink data and response signals for downlink data simultaneously in theuplink. In this situation, the response signals and uplink data from theterminals are transmitted using time-division multiplexing (TDM). Asdescribed above, the single carrier properties of transmission waveformsof the terminals are maintained by the simultaneous transmission ofresponse signals and uplink data using TDM.

In addition, as illustrated in FIG. 2, the response signals (i.e.,“A/N”) transmitted from each terminal partially occupy the resourcesassigned to uplink data (i.e., Physical Uplink Shared CHannel (PUSCH)resources) (i.e., response signals occupy some SC-FDMA symbols adjacentto SC-FDMA symbols to which reference signals (RS) are mapped) and arethereby transmitted to a base station in time-division multiplexing(TDM). However, “subcarriers” in the vertical axis in FIG. 2 are alsotermed as “virtual subcarriers” or “time contiguous signals,” and “timecontiguous signals” that are collectively inputted to a discrete Fouriertransform (DFT) circuit in a SC-FDMA transmitter are represented as“subcarriers” for convenience. To put it more specifically, optionaldata of the uplink data is punctured due to the response signals in thePUSCH resources. Accordingly, the quality of uplink data (e.g., codinggain) is significantly reduced due to the punctured bits of the codeduplink data. For this reason, base stations instruct the terminals touse a very low coding rate and/or to use very large transmission powerso as to compensate for the reduced quality of the uplink data due tothe puncturing.

Meanwhile, the standardization of 3GPP LTE-Advanced for realizing fastercommunication than 3GPP LTE is in progress. 3GPP LTE-Advanced systems(may be referred to as “LTE-A system,” hereinafter) follow LTE systems.3GPP LTE-Advanced will introduce base stations and terminals capable ofcommunicating with each other using a wideband frequency of 40 MHz orgreater to realize a downlink transmission rate of up to 1 Gbps orabove.

In the LTE-A system, in order to simultaneously achieve backwardcompatibility with the LTE system and ultra-high-speed communicationseveral times faster than transmission rates in the LTE system, theLTE-A system band is divided into “component carriers” of 20 MHz orbelow, which is the bandwidth supported by the LTE system. In otherwords, the “component carrier” is defined herein as a band having amaximum width of 20 MHz and as the basic unit of communication band. Inthe Frequency Division Duplex (FDD) system, moreover, “componentcarrier” in downlink (hereinafter, referred to as “downlink componentcarrier”) is defined as a band obtained by dividing a band according todownlink frequency bandwidth information in a BCH broadcasted from abase station or as a band defined by a distribution width when adownlink control channel (PDCCH) is distributed in the frequency domain.In addition, “component carrier” in uplink (hereinafter, referred to as“uplink component carrier”) may be defined as a band obtained bydividing a band according to uplink frequency band information in a BCHbroadcasted from a base station or as the basic unit of a communicationband of 20 MHz or below including a Physical Uplink Shared CHannel(PUSCH) in the vicinity of the center of the bandwidth and PUCCHs forLTE on both ends of the band. In addition, the term “component carrier”may be also referred to as “cell” in English in 3GPP LTE-Advanced.Furthermore, “component carrier” may also be abbreviated as CC(s).

In the Time Division Duplex (TDD) system, a downlink component carrierand an uplink component carrier have the same frequency band, anddownlink communication and uplink communication are realized byswitching between the downlink and uplink on a time division basis. Forthis reason, in the case of the TDD system, the downlink componentcarrier can also be expressed as “downlink communication timing in acomponent carrier.” The uplink component carrier can also be expressedas “uplink communication timing in a component carrier.” The downlinkcomponent carrier and the uplink component carrier are switched based ona UL-DL configuration as shown in FIG. 3. In the UL-DL configurationshown in FIG. 3, timings are configured in subframe units (that is, 1msec units) for downlink communication (DL) and uplink communication(UL) per frame (10 msec). The UL-DL configuration can construct acommunication system capable of flexibly meeting a downlinkcommunication throughput requirement and an uplink communicationthroughput requirement by changing a subframe ratio between downlinkcommunication and uplink communication. For example, FIG. 3 illustratesUL-DL configurations (Config 0 to 6) having different subframe ratiosbetween downlink communication and uplink communication. In addition, inFIG. 3, a downlink communication subframe is represented by “D,” anuplink communication subframe is represented by “U” and a specialsubframe is represented by “S.” Here, the special subframe is a subframeat the time of switchover from a downlink communication subframe to anuplink communication subframe. In the special subframe, downlink datacommunication may be performed as in the case of the downlinkcommunication subframe. In each UL-DL configuration shown in FIG. 3,subframes (20 subframes) corresponding to 2 frames are expressed in twostages: subframes (“D” and “S” in the upper row) used for downlinkcommunication and subframes (“U” in the lower row) used for uplinkcommunication. Furthermore, as shown in FIG. 3, an error detectionresult corresponding to downlink data (ACK/NACK) is reported in thefourth uplink communication subframe or an uplink communication subframeafter the fourth subframe after the subframe to which the downlink datais assigned.

The LTE-A system supports communication using a band obtained bybundling some component carriers, so-called carrier aggregation (CA).Note that while a UL-DL configuration can be set for each componentcarrier, an LTE-A system compliant terminal (hereinafter, referred to as“LTE-A terminal”) is designed assuming that the same UL-DL configurationis set among a plurality of component carriers.

FIGS. 4A and 4B are diagrams provided for describing asymmetric carrieraggregation and a control sequence thereof applicable to individualterminals.

As illustrated in FIG. 4B, a configuration in which carrier aggregationis performed using two downlink component carriers and one uplinkcomponent carrier on the left is set for terminal 1, while aconfiguration in which the two downlink component carriers identicalwith those used by terminal 1 are used but uplink component carrier onthe right is used for uplink communication is set for terminal 2.

Referring to terminal 1, a base station included an LTE-A system (thatis, LTE-A system compliant base station (hereinafter, referred to as“LTE-A base station”) and an LTE-A terminal included in the LTE-A systemtransmit and receive signals to and from each other in accordance withthe sequence diagram illustrated in FIG. 4A. As illustrated in FIG. 4A,(1) terminal 1 is synchronized with the downlink component carrier onthe left when starting communications with the base station and readsinformation on the uplink component carrier paired with the downlinkcomponent carrier on the left from a broadcast signal called systeminformation block type 2 (SIB2). (2) Using this uplink componentcarrier, terminal 1 starts communication with the base station bytransmitting, for example, a connection request to the base station. (3)Upon determining that a plurality of downlink component carriers need tobe assigned to the terminal, the base station instructs the terminal toadd a downlink component carrier. However, in this case, the number ofuplink component carriers does not increase, and terminal 1, which is anindividual terminal, starts asymmetric carrier aggregation.

In addition, in the LTE-A system to which carrier aggregation isapplied, a terminal may receive a plurality of pieces of downlink dataon a plurality of downlink component carriers at a time. In LTE-A,channel selection (also referred to as “multiplexing”), bundling and adiscrete Fourier transform spread orthogonal frequency divisionmultiplexing (DFT-S-OFDM) format are available as a method oftransmitting a plurality of response signals for the plurality of piecesof downlink data. In channel selection, a terminal causes not onlysymbol points used for response signals, but also the resources to whichthe response signals are mapped to vary in accordance with the patternfor results of the error detection on the plurality of pieces ofdownlink data. Compared with channel selection, in bundling, theterminal bundles ACK or NACK signals generated according to the resultsof error detection on the plurality of pieces of downlink data (i.e., bycalculating a logical AND of the results of error detection on theplurality of pieces of downlink data, provided that ACK=1 and NACK=0),and response signals are transmitted using one predetermine resource. Intransmission using the DFT-S-OFDM format, a terminal jointly encodes(i.e., joint coding) the response signals for the plurality of pieces ofdownlink data and transmits the coded data using the format (see, NPL5). For example, a terminal may feed back the response signals (i.e.,ACK/NACK) using channel selection, bundling or DFT-S-OFDM according tothe number of bits for a pattern for results of error detection.Alternatively, a base station may previously configure the method oftransmitting the response signals.

Channel Selection is a technique that varies not only the phase points(i.e., constellation points) for the response signals but also theresources used for transmission of the response signals (may be referredto as “PUCCH resource,” hereinafter) on the basis of whether the resultsof error detection on the plurality of pieces of downlink data for eachdownlink component carrier received on the plurality of downlinkcomponent carriers (a maximum of two downlink component carriers) areeach an ACK or NACK as illustrated in FIG. 5. Meanwhile, bundling is atechnique that bundles ACK/NACK signals for the plurality of pieces ofdownlink data into a single set of signals and thereby transmits thebundled signals using one predetermined resource (see, NPLs 6 and 7).Hereinafter, the set of the signals formed by bundling ACK/NACK signalsfor a plurality of pieces of downlink data into a single set of signalsmay be referred to as “bundled ACK/NACK signals.”

The following two methods are considered as a possible method oftransmitting response signals in uplink when a terminal receivesdownlink assignment control information via a PDCCH and receivesdownlink data.

One of the methods is to transmit response signals using a PUCCHresource associated in a one-to-one correspondence with a controlchannel element (CCE) occupied by the PDCCH (i.e., implicit signaling)(hereinafter, method 1). More specifically, when DCI intended for aterminal served by a base station is mapped in a PDCCH region, eachPDCCH occupies a resource consisting of one or a plurality of contiguousCCEs. In addition, as the number of CCEs occupied by a PDCCH (i.e., thenumber of aggregated CCEs: CCE aggregation level), one of aggregationlevels 1, 2, 4 and 8 is selected according to the number of informationbits of the assignment control information or a propagation pathcondition of the terminal, for example.

The other method is to previously indicate a PUCCH resource to eachterminal from a base station (i.e., explicit signaling) (hereinafter,method 2). To put it differently, each terminal transmits responsesignals using the PUCCH resource previously indicated by the basestation in method 2.

Furthermore, as shown in FIG. 5, the terminal transmits response signalsusing one of two component carriers. A component carrier that transmitssuch response signals is called “primary component carrier (PCC) orprimary cell (PCell).” The other component carrier is called “secondarycomponent carrier (SCC) or secondary cell (SCell).” For example, the PCC(PCell) is a component carrier that transmits broadcast information on acomponent carrier that transmits response signals (e.g., systeminformation block type 2 (SIB2)).

In method 2, PUCCH resources common to a plurality of terminals (e.g.,four PUCCH resources) may be previously indicated to the terminals froma base station. For example, terminals may employ a method to select onePUCCH resource to be actually used, on the basis of a transmit powercontrol (TPC) command of two bits included in DCI in SCell. In thiscase, the TPC command is also called an ACK/NACK resource indicator(ARI). Such a TPC command allows a certain terminal to use an explicitlysignaled PUCCH resource in a certain subframe while allowing anotherterminal to use the same explicitly signaled PUCCH resource in anothersubframe in the case of explicit signaling.

Meanwhile, in channel selection, a PUCCH resource in an uplink componentcarrier associated in a one-to-one correspondence with the top CCE indexof the CCEs occupied by the PDCCH indicating the PDSCH in PCC (PCell)(i.e., PUCCH resource in PUCCH region 1 in FIG. 5) is assigned (implicitsignaling).

Here, ARQ control using channel selection when the above asymmetriccarrier aggregation is applied to a terminal will be described withreference to FIG. 5 and FIGS. 6A and 6B.

For example, in FIG. 5, a component carrier group (may be referred to as“component carrier set” in English) consisting of component carrier 1(PCell) and component carrier 2 (SCell) is set for terminal 1. In thiscase, after downlink resource assignment information is transmitted toterminal 1 from the base station via a PDCCH of each of componentcarriers 1 and 2, downlink data is transmitted using the resourcecorresponding to the downlink resource assignment information.

Furthermore, in channel selection, response signals representing errordetection results corresponding to a plurality of pieces of downlinkdata in component carrier 1 (PCell) and error detection resultscorresponding to a plurality of pieces of downlink data in componentcarrier 2 (SCell) are mapped to PUCCH resources included in PUCCH region1 or PUCCH region 2. The terminal uses two types of phase points (BinaryPhase Shift Keying (BPSK) mapping) or four types of phase points(Quadrature Phase Shift Keying (QPSK) mapping) as response signalsthereof. That is, in channel selection, it is possible to express apattern for results of error detection corresponding to a plurality ofpieces of downlink data in component carrier 1 (PCell) and the resultsof error detection corresponding to a plurality of pieces of downlinkdata in component carrier 2 (SCell) by a combination of PUCCH resourcesand phase points.

Here, FIG. 6A shows a method of mapping a pattern for results of errordetection when the number of component carriers is two (one PCell, oneSCell) in a TDD system.

Note that FIG. 6A assumes a case where the transmission mode is set toone of (a), (b) and (c) below.

(a) A transmission mode in which each component carrier supports onlyone-CW transmission in downlink

(b) A transmission mode in which one component carrier supports onlyone-CW transmission in downlink and the other component carrier supportsup to two-CW transmission in downlink

(c) A transmission mode in which each component carrier supports up totwo-CW transmission in downlink

Furthermore, FIG. 6A assumes a case where number M is set in one of (1)to (4) below, M indicating how many downlink communication subframes percomponent carrier (hereinafter, described as “DL (DownLink) subframes,”“D” or “S” shown in FIG. 3) of results of error detection need to bereported to the base station using one uplink communication subframe(hereinafter, described as “UL (UpLink) subframe,” “U” shown in FIG. 3).For example, in Config 2 shown in FIG. 3, since results of errordetection of four DL subframes are reported to the base station usingone UL subframe, M=4.

(1) M=1

(2) M=2

(3) M=3

(4) M=4

That is, FIG. 6A illustrates a method of mapping a pattern for resultsof error detection when (a) to (c) above are combined with (1) to (4)above. The value of M varies depending on UL-DL configuration (Config 0to 6) and subframe number (SF #0 to SF #9) in one frame as shown in FIG.3. Furthermore, in Config 5 shown in FIG. 3, M=9 in subframe (SF) #2.However, in this case, in the LTE-A TDD system, the terminal does notapply channel selection and reports the results of error detectionusing, for example, a DFT-S-OFDM format. For this reason, in FIG. 6A,Config 5 (M=9) is not included in the combination.

In the case of (1), the number of error detection result patterns is2²×1=4 patterns, 2³×1=8 patterns and 2⁴×1=16 patterns in order of (a),(b) and (c). In the case of (2), the number of error detection resultpatterns is 2²×2=8 patterns, 2³×2=16 patterns, 2⁴×2=32 patterns in orderof (a), (b) and (c). The same applies to (3) and (4).

Here, it is assumed that the phase difference between phase points to bemapped in one PUCCH resource is 90 degrees at minimum (that is, a casewhere a maximum of 4 patterns per PUCCH resource are mapped). In thiscase, the number of PUCCH resources necessary to map all error detectionresult patterns is 2⁴×4−4=16 in (4) and (c) when the number of errordetection result patterns is a maximum (2⁴×4=64 patterns), which is notrealistic. Thus, the TDD system intentionally reduces the amount ofinformation on the results of error detection by bundling the results oferror detection in a spatial region or further in a time domain ifnecessary. In this way, the TDD system limits the number of PUCCHresources necessary to report the error detection result patterns.

In the LTE-A TDD system, in the case of (1), the terminal maps 4patterns, 8 patterns and 16 patterns of results of error detection inorder of (a), (b) and (c) to 2, 3 and 4 PUCCH resources respectivelywithout bundling the results of error detection (Step3 in FIG. 6A). Thatis, the terminal reports an error detection result using 1 bit percomponent carrier in which a transmission mode (non-MIMO) supportingonly one-codeword (CW) transmission in downlink and reports errordetection results using 2 bits per component carrier in which atransmission mode (MIMO) supporting up to two-CW transmissions indownlink.

In the LTE-A TDD system, in the cases of (2) and (a), the terminal mapseight patterns of results of error detection to four PUCCH resourceswithout bundling the results of error detection (Step3 in FIG. 6A). Inthat case, the terminal reports error detection results using 2 bits perdownlink component carrier.

In the LTE-A TDD system, in the cases of (2) and (b) (the same appliesto (2) and (c)), the terminal bundles the results of error detection ofcomponent carriers in which a transmission mode supporting up to two-CWtransmission in downlink is set in a spatial region (spatial bundling)(Step1 in FIG. 6A). In the spatial bundling, when the result of errordetection corresponding to at least one CW of two CWs of the results oferror detection is NACK, the terminal determines the results of errordetection after the spatial bundling to be NACK. That is, in spatialbundling, Logical And of the results of error detection of two CWs istaken. The terminal then maps error detection result patterns afterspatial bundling (8 patterns in the cases of (2) and (b), 16 patterns inthe cases of (2) and (c)) to four PUCCH resources (Step3 in FIG. 6A). Inthat case, the terminal reports error detection results using 2 bits perdownlink component carrier.

In the LTE-A TDD system, in the cases of (3) or (4), and (a), (b) or(c), the terminal performs bundling in the time domain (time-domainbundling) after the spatial bundling (Step1) (Step2 in FIG. 6A). Theterminal then maps the error detection result patterns after thetime-domain bundling to four PUCCH resources (Step3 in FIG. 6A). In thatcase, the terminal reports results of error detection using 2 bits perdownlink component carrier.

Next, an example of more specific mapping methods will be described withreference to FIG. 6B. FIG. 6B shows an example of a case where thenumber of downlink component carriers is 2 (one PCell, one SCell) and acase where “(c) a transmission mode in which each component carriersupports up to two-CW transmission in the downlink” is set and a casewith “(4) M=4.”

In FIG. 6B, the results of error detection of a PCell are (ACK (A),ACK), (ACK, ACK), (NACK (N), NACK) and (ACK, ACK) in order of (CW0, CW1)in four DL subframes (SF1 to 4). In the PCell shown in FIG. 6B, M=4, andtherefore the terminal spatially bundles these subframes in Step in FIG.6A (portions enclosed by a solid line in FIG. 6B). As a result of thespatial bundling, ACK, ACK, NACK and ACK are obtained in that order infour DL subframes of the PCell shown in FIG. 6B. Furthermore, in Step2in FIG. 6A, the terminal applies time-domain bundling to the 4-bit errordetection result pattern (ACK, ACK, NACK, ACK) after spatial bundlingobtained in Step1 (portions enclosed by broken line in FIG. 6B). In thisway, a 2-bit error detection result of (NACK, ACK) is obtained in thePCell shown in FIG. 6B.

The terminal likewise applies spatial bundling and time-domain bundlingalso for the SCell shown in FIG. 6B and thereby obtains a 2-bit errordetection result (NACK, NACK).

The terminal then combines the error detection result patterns using 2bits each after time-domain bundling of the PCell and SCell in Step3 inFIG. 6A in order of the PCell, SCell to bundle them into a 4-bit errordetection result pattern (NACK, ACK, NACK, NACK). The terminaldetermines a PUCCH resource (in this case, h1) and a phase point (inthis case, -j) using the mapping table shown in Step3 in FIG. 6A fromthis 4-bit error detection result pattern.

CITATION LIST Non-Patent Literatures

NPL 1

-   3GPP TS 36.211 V10.1.0, “Physical Channels and Modulation (Release    9),” March 2011

NPL 2

-   3GPP TS 36.212 V10.1.0, “Multiplexing and channel coding (Release    9),” March 2011

NPL 3

-   3GPP TS 36.213 V10.1.0, “Physical layer procedures (Release 9),”    March 2011

NPL 4

-   Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko    Hiramatsu, “Performance enhancement of E-UTRA uplink control channel    in fast fading environments,” Proceeding of IEEE VTC 2009 spring,    April. 2009

NPL 5

-   Ericsson and ST-Ericsson, “A/N transmission in the uplink for    carrier aggregation,” R1-100909, 3GPP TSG-RAN WG1 #60, February 2010

NPL 6

-   ZTE, 3GPP RAN1 meeting #57, R1-091702, “Uplink Control Channel    Design for LTE-Advanced,” May 2009

NPL 7

-   Panasonic, 3GPP RAN1 meeting #57, R1-091744, “UL ACK/NACK    transmission on PUCCH for Carrier aggregation,” May 2009

SUMMARY OF INVENTION Technical Problem

As described above, LTE-A terminals are designed on the assumption thatthe same UL-DL configuration is set among a plurality of componentcarriers. This is because carrier aggregation among a plurality ofcomponent carriers (e.g., a certain 20 MHz bandwidth and a different 20MHz bandwidth in a 2 GHz band, for example) in one frequency band (e.g.,2 GHz band) (so-called intra-band carrier aggregation) is conventionallyassumed. When uplink communication and downlink communication aresimultaneously performed between different component carriers in thesame frequency band, a terminal in downlink communication receives largeinterference from a terminal carrying out uplink communication. On theother hand, there is a large frequency gap in carrier aggregation amongcomponent carriers of a plurality of frequency bands (e.g., 2 GHz bandand 800 MHz band) (e.g., a certain 20 MHz bandwidth in a 2 GHz band anda certain 20 MHz bandwidth in an 800 MHz band) (so-called inter-bandcarrier aggregation). Thus, interference received by a terminal indownlink communication using a component carrier of a certain frequencyband (e.g., 20 MHz bandwidth in a 2 GHz band) from another terminal inuplink communication in another frequency band (e.g., 20 MHz bandwidthin an 800 MHz band) is small.

Incidentally, studies are being carried out, for a case where acommunication carrier providing an LTE-A TDD system newly assigns afrequency band to an LTE-A service, on a possibility of varying a UL-DLconfiguration of the newly assigned frequency band from a UL-DLconfiguration of an existing frequency band depending on a service towhich the communication carrier attaches greater importance. To be morespecific, a communication carrier that attaches greater importance todownlink communication throughput uses a UL-DL configuration having agreater ratio of DL subframes to UL subframes in a new frequency band(e.g., Config 3, 4 or 5 or the like in FIG. 3). This allows a moreflexible system to be constructed.

However, no studies have been carried out so far on a method of bundlingresults of error detection when a UL-DL configuration varies betweencomponent carriers, that is, when the value of “M” varies from onecomponent carrier to another.

FIG. 7A and FIG. 7B illustrate an example of a method of reportingresults of error detection when a UL-DL configuration varies betweencomponent carriers. For example, in FIG. 7A and FIG. 7B, a componentcarrier (frequency f1) in which Config 2 is set is a PCell and acomponent carrier (frequency f2) in which Config 3 is set is an SCell.

FIG. 7A illustrates a method of reporting results of error detectionusing component carriers of the PCell and SCell independently. Accordingto the method in FIG. 7A, since the terminal can independently reportresults of error detection for each component carrier, the degree ofcomplexity is low. However, in FIG. 7A, resources (A/N resources) totransmit results of error detection (response signals) are required foreach of the two component carriers. Moreover, in FIG. 7A, a base stationneeds to perform a decoding processing on results of error detection ofthe two component carriers in parallel (that is, 2-parallel). That is,in FIG. 7A, A/N resources and decoding processing two times as large asthose of 3GPP Release 10 (Rel-10) in which only one component carrier (1CC) is set for a terminal are required.

Furthermore, when a terminal is configured with a maximum of 5 CCs, A/Nresources corresponding to a maximum of 5 CCs are required. Furthermore,the base station requires decoding processing on results of errordetection in a maximum of 5 CCs in-parallel (1 CC error detectionresult/1 parallel). Here, when a UL-DL configuration is always the sameamong component carriers, UL subframe timings are the same among thecomponent carriers. Thus, even when a terminal is configured with amaximum of 5 CCs of component carriers, the required A/N resource amountis only A/N resources corresponding to 1 CC. Moreover, decodingprocessing on results of error detection in the base station required isalso only a 1-parallel process (process on 1-CC error detection result)when up to 5 CCs are set. In contrast, when a UL-DL configuration variesamong component carriers, a maximum of quintuple A/N resources anddecoding processing amount are required.

On the other hand, FIG. 7B illustrates a method of reporting results oferror detection of the component carriers always bundled in a PCell.That is, in FIG. 7B, results of error detection of both the PCell andSCell are transmitted in UL subframes of the PCell. Since the terminalalways reports results of error detection from the PCell in the methodin FIG. 7B, A/N resources used are only ones corresponding to 1 CC ofthe PCell. Furthermore, decoding processing on results of errordetection required in the base station is also only a 1-parallel process(up to 5-CC error detection results/1 parallel).

However, timing of reporting results of error detection of the SCell mayvary compared to the case with 1 CC depending on a combination of UL-DLconfigurations respectively set in the PCell and SCell. For example, inFIG. 7B, the earliest indication timing for an error detection result ofdata in subframe #0 of the SCell in which Config 3 is set is subframe #7of the PCell. However, as shown in FIG. 3, when Config 3 is set only ina single component carrier (1 CC), the indication timing correspondingto the results of error detection for data in subframe #0 is subframe#4. Thus, when the timing of reporting results of error detection variesdepending on the combination of UL-DL configurations, processes becomesvery complicated and the number of test cases increases.

An object of the present invention is to provide, when ARQ is applied tocommunication using an uplink component carrier and a plurality ofdownlink component carriers associated with the uplink component carrierand when a UL-DL configuration (ratio between UL and DL subframes) setfor each component carrier varies, a terminal apparatus and atransmission method capable of suppressing increases in the A/N resourceamount used and the amount of decoding processing on results of errordetection in a base station without changing timing of reporting resultsof error detection of an SCell from timing of reporting results of errordetection when only a single component carrier is set.

Solution to Problem

A terminal apparatus according to an aspect of the present invention isconfigured to communicate with a base station apparatus using aplurality of component carriers in each of which a configuration patternof subframes forming one frame is set, the configuration patternincluding a downlink communication subframe used for downlinkcommunication and an uplink communication subframe used for uplinkcommunication, the terminal apparatus including: a receiving sectionthat receives downlink data pieces using the plurality of componentcarriers, respectively; an error detection section that detects an errorof each of the downlink data pieces; a generating section that generatesa response signal using an error detection result of each of thedownlink data pieces obtained by the error detection section; and acontrol section that transmits the response signal to the base stationapparatus, in which: the control section transmits, using a firstcomponent carrier, a response signal including error detection resultsfor the data pieces respectively received using the first componentcarrier and a second component carrier among the plurality of componentcarriers; and in a first configuration pattern that is set in the firstcomponent carrier, at least an uplink communication subframe is set at atiming identical to that of an uplink communication subframe of a secondconfiguration pattern that is set in the second component carrier.

A transmission method according to an aspect of the present invention isused in a terminal apparatus configured to communicate with a basestation apparatus using a plurality of component carriers in each ofwhich a configuration pattern of subframes forming one frame is set, theconfiguration pattern including a downlink communication subframe usedfor downlink communication and an uplink communication subframe used foruplink communication, the method including: receiving downlink datapieces using the plurality of component carriers, respectively;detecting an error of each of the downlink data pieces; generating aresponse signal using an error detection result of each of the downlinkdata pieces to be obtained; and transmitting the response signal to thebase station apparatus, in which: the control section transmits, using afirst component carrier, a response signal including error detectionresults for the data pieces respectively received using the firstcomponent carrier and a second component carrier among the plurality ofcomponent carriers; and in a first configuration pattern that is set inthe first component carrier, at least an uplink communication subframeis set at a timing identical to that of an uplink communication subframeof a second configuration pattern that is set in the second componentcarrier.

Advantageous Effects of Invention

According to the present invention, when ARQ is applied to communicationusing an uplink component carrier and a plurality of downlink componentcarriers associated with the uplink component carrier, and when a UL-DLconfiguration (ratio between UL subframes and DL subframes) set for eachcomponent carrier varies, it is possible to suppress increases in theA/N resource amount used and the amount of decoding processing onresults of error detection in a base station without changing timing ofreporting results of error detection of an SCell from timing ofreporting results of error detection when only a single componentcarrier is set.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a method of spreading response signalsand reference signals;

FIG. 2 is a diagram illustrating an operation related to a case whereTDM is applied to response signals and uplink data on PUSCH resources;

FIG. 3 is a diagram provided for describing a UL-DL configuration inTDD;

FIGS. 4A and 4B are diagrams provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals;

FIG. 5 is a diagram provided for describing channel selection;

FIGS. 6A and 6B are diagrams provided for describing a bundling methodand a mapping method in TDD;

FIGS. 7A and 7B illustrate a method of reporting response signals when aUL-DL configuration varies between component carriers;

FIG. 8 is a block diagram illustrating a main configuration of aterminal according to Embodiment 1 of the present invention;

FIG. 9 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 10 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 11 illustrates a method of grouping component carriers according toEmbodiment 1 of the present invention;

FIGS. 12A and 12B illustrate an inclusion relation between UL-DLconfigurations according to Embodiment 2 of the present invention;

FIGS. 13A and 13B illustrate timing of transmitting response signalsaccording to Embodiment 2 of the present invention;

FIGS. 14A to 14C illustrate processes when a component carrier is addedto the terminal according to Embodiment 2 of the present invention;

FIGS. 15A and 15B illustrate a group number signaling method accordingto Embodiment 2 of the present invention (setting method 1);

FIG. 16 illustrates a group number signaling method according toEmbodiment 2 of the present invention (setting method 2);

FIGS. 17A and 17B are diagrams provided for describing problemsaccording to Embodiment 3 of the present invention;

FIGS. 18A and 18B illustrate an inclusion relation between UL-DLconfigurations according to Embodiment 3 of the present invention;

FIGS. 19A to 19C illustrate a method of grouping component carriersaccording to Embodiment 3 of the present invention;

FIG. 20 illustrates another variation of the present invention;

FIGS. 21A and B illustrate a further variation of the present invention;

FIG. 22 illustrates a still further variation of the present invention;

FIGS. 23A and 23B illustrate a UL-DL configuration of a terminalaccording to Embodiment 4 of the present invention;

FIG. 24 illustrates UL-DL configuration settings that satisfy condition(1) according to Embodiment 4 of the present invention;

FIGS. 25A and 25B are diagrams provided for describing problems with CRSmeasurement according to Embodiment 4 of the present invention;

FIG. 26 illustrates UL-DL configuration settings that satisfy condition(1) and condition (2) according to Embodiment 4 of the presentinvention;

FIG. 27 is a diagram provided for describing problems with SRStransmission according to Embodiment 4 of the present invention;

FIG. 28 illustrates UL-DL configuration settings that satisfy condition(3) according to Embodiment 4 of the present invention;

FIGS. 29A and 29B are diagrams provided for describing problems with CRSmeasurement according to Embodiment 5 of the present invention;

FIG. 30 illustrates UL-DL configuration settings that satisfy condition(2) according to Embodiment 5 of the present invention; and

FIG. 31 is a diagram provided for describing problems with SRStransmission according to Embodiment 5 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the claimed invention will be described indetail with reference to the accompanying drawings. Throughout theembodiments, the same elements are assigned the same reference numeralsand any duplicate description of the elements is omitted.

Embodiment 1

FIG. 8 is a main configuration diagram of terminal 200 according to thepresent embodiment. Terminal 200 communicates with base station 100using a plurality of component carriers including a first componentcarrier and a second component carrier. Furthermore, as a configurationpattern of subframes making up one frame, the configuration patternincluding downlink communication subframes (DL subframes) used fordownlink communication and uplink communication subframes (UL subframes)used for uplink communication (DL-UL Configuration) is set in eachcomponent carrier set for terminal 200. In terminal 200, extractionsection 204 receives downlink data using a plurality of componentcarriers; CRC section 211 detects an error of each piece of downlinkdata; response signal generating section 212 generates a response signalusing the result of error detection of each piece of downlink dataobtained in CRC section 211; and control section 208 transmits theresponse signal to base station 100. However, in the UL DL configuration(first configuration pattern) set in a first component carrier, ULsubframes are configured at the same timings as those of UL subframes ofthe UL DL configuration (second configuration pattern) set in at least asecond component carrier. Furthermore, control section 208 transmits,using the first component carrier, response signals including results oferror detection corresponding to data received by each of the firstcomponent carrier and second component carrier.

(Configuration of Base Station)

FIG. 9 is a configuration diagram of base station 100 according toEmbodiment 1 of the claimed invention. In FIG. 9, base station 100includes control section 101, control information generating section102, coding section 103, modulation section 104, coding section 105,data transmission controlling section 106, modulation section 107,mapping section 108, inverse fast Fourier transform (IFFT) section 109,CP adding section 110, radio transmitting section 111, radio receivingsection 112, CP removing section 113, PUCCH extracting section 114,despreading section 115, sequence controlling section 116, correlationprocessing section 117, A/N determining section 118, bundled A/Ndespreading section 119, inverse discrete Fourier transform (IDFT)section 120, bundled A/N determining section 121 and retransmissioncontrol signal generating section 122.

Control section 101 assigns a downlink resource for transmitting controlinformation (i.e., downlink control information assignment resource) anda downlink resource for transmitting downlink data (i.e., downlink dataassignment resource) for a resource assignment target terminal(hereinafter, referred to as “destination terminal” or simply“terminal”) 200. This resource assignment is performed in a downlinkcomponent carrier included in a component carrier group configured forresource assignment target terminal 200. In addition, the downlinkcontrol information assignment resource is selected from among theresources corresponding to downlink control channel (i.e., PDCCH) ineach downlink component carrier. Moreover, the downlink data assignmentresource is selected from among the resources corresponding to downlinkdata channel (i.e., PDSCH) in each downlink component carrier. Inaddition, when there are a plurality of resource assignment targetterminals 200, control section 101 assigns different resources toresource assignment target terminals 200, respectively.

The downlink control information assignment resources are equivalent toL1/L2 CCH described above. To put it more specifically, the downlinkcontrol information assignment resources are each formed of one or aplurality of CCEs.

Control section 101 determines the coding rate used for transmittingcontrol information to resource assignment target terminal 200. The datasize of the control information varies depending on the coding rate.Thus, control section 101 assigns a downlink control informationassignment resource having the number of CCEs that allows the controlinformation having this data size to be mapped to the resource.

Control section 101 outputs information on the downlink data assignmentresource to control information generating section 102. Moreover,control section 101 outputs information on the coding rate to codingsection 103. In addition, control section 101 determines and outputs thecoding rate of transmission data (i.e., downlink data) to coding section105. Moreover, control section 101 outputs information on the downlinkdata assignment resource and downlink control information assignmentresource to mapping section 108. However, control section 101 controlsthe assignment in such a way that the downlink data and downlink controlinformation for the downlink data are mapped to the same downlinkcomponent carrier.

Control information generating section 102 generates and outputs controlinformation including the information on the downlink data assignmentresource to coding section 103. This control information is generatedfor each downlink component carrier. In addition, when there are aplurality of resource assignment target terminals 200, the controlinformation includes the terminal ID of each destination terminal 200 inorder to distinguish resource assignment target terminals 200 from oneanother. For example, the control information includes CRC bits maskedby the terminal ID of destination terminal 200. This control informationmay be referred to as “control information carrying downlink assignment”or “downlink control information (DCI).”

Coding section 103 encodes the control information using the coding ratereceived from control section 101 and outputs the coded controlinformation to modulation section 104.

Modulation section 104 modulates the coded control information andoutputs the resultant modulation signals to mapping section 108.

Coding section 105 uses the transmission data (i.e., downlink data) foreach destination terminal 200 and the coding rate information fromcontrol section 101 as input and encodes and outputs the transmissiondata to data transmission controlling section 106. However, when aplurality of downlink component carriers are assigned to destinationterminal 200, coding section 105 encodes each piece of transmission datato be transmitted on a corresponding one of the downlink componentcarriers and transmits the coded pieces of transmission data to datatransmission controlling section 106.

Data transmission controlling section 106 outputs the coded transmissiondata to modulation section 107 and also keeps the coded transmissiondata at the initial transmission. In addition, data transmissioncontrolling section 106 keeps the transmission data for one destinationterminal 200 for each downlink component carrier on which thetransmission data is transmitted. Thus, it is possible to perform notonly retransmission control for overall data transmitted to destinationterminal 200, but also retransmission control for data on each downlinkcomponent carrier.

Furthermore, upon reception of a NACK or DTX for downlink datatransmitted on a certain downlink component carrier from retransmissioncontrol signal generating section 122, data transmission controllingsection 106 outputs the data kept in the manner described above andcorresponding to this downlink component carrier to modulation section107. Upon reception of an ACK for the downlink data transmitted on acertain downlink component carrier from retransmission control signalgenerating section 122, data transmission controlling section 106deletes the data kept in the manner described above and corresponding tothis downlink component carrier.

Modulation section 107 modulates the coded transmission data receivedfrom data transmission controlling section 106 and outputs the resultantmodulation signals to mapping section 108.

Mapping section 108 maps the modulation signals of the controlinformation received from modulation section 104 to the resourceindicated by the downlink control information assignment resourcereceived from control section 101 and outputs the resultant modulationsignals to IFFT section 109.

Mapping section 108 maps the modulation signals of the transmission datareceived from modulation section 107 to the resource (i.e., PDSCH (i.e.,downlink data channel)) indicated by the downlink data assignmentresource received from control section 101 (i.e., information includedin the control information) and outputs the resultant modulation signalsto IFFT section 109.

The control information and transmission data mapped to a plurality ofsubcarriers in a plurality of downlink component carriers in mappingsection 108 is transformed into time-domain signals fromfrequency-domain signals in IFFT section 109, and CP adding section 110adds a CP to the time-domain signals to form OFDM signals. The OFDMsignals undergo transmission processing such as digital to analog (D/A)conversion, amplification and up-conversion and/or the like in radiotransmitting section 111 and are transmitted to terminal 200 via anantenna.

Radio receiving section 112 receives, via an antenna, the uplinkresponse signals or reference signals transmitted from terminal 200, andperforms reception processing such as down-conversion, A/D conversionand/or the like on the uplink response signals or reference signals.

CP removing section 113 removes the CP added to the uplink responsesignals or reference signals from the uplink response signals orreference signals that have undergone the reception processing.

PUCCH extracting section 114 extracts, from the PUCCH signals includedin the received signals, the signals in the PUCCH region correspondingto the bundled ACK/NACK resource previously indicated to terminal 200.The bundled ACK/NACK resource herein refers to a resource used fortransmission of the bundled ACK/NACK signals and adopting the DFT-S-OFDMformat structure. To put it more specifically, PUCCH extracting section114 extracts the data part of the PUCCH region corresponding to thebundled ACK/NACK resource (i.e., SC-FDMA symbols on which the bundledACK/NACK resource is assigned) and the reference signal part of thePUCCH region (i.e., SC-FDMA symbols on which the reference signals fordemodulating the bundled ACK/NACK signals are assigned). PUCCHextracting section 114 outputs the extracted data part to bundled A/Ndespreading section 119 and outputs the reference signal part todespreading section 115-1.

In addition, PUCCH extracting section 114 extracts, from the PUCCHsignals included in the received signals, a plurality of PUCCH regionscorresponding to an A/N resource associated with a CCE that has beenoccupied by the PDCCH used for transmission of the downlink assignmentcontrol information (DCI), and corresponding to a plurality of A/Nresources previously indicated to terminal 200. The A/N resource hereinrefers to the resource to be used for transmission of an A/N. To put itmore specifically, PUCCH extracting section 114 extracts the data partof the PUCCH region corresponding to the A/N resource (i.e., SC-FDMAsymbols on which the uplink control signals are assigned) and thereference signal part of the PUCCH region (i.e., SC-FDMA symbols onwhich the reference signals for demodulating the uplink control signalsare assigned). PUCCH extracting section 114 outputs both of theextracted data part and reference signal part to despreading section115-2. In this manner, the response signals are received on the resourceselected from the PUCCH resource associated with the CCE and thespecific PUCCH resource previously indicated to terminal 200.

Sequence controlling section 116 generates a base sequence that may beused for spreading each of the A/N reported from terminal 200, thereference signals for the A/N, and the reference signals for the bundledACK/NACK signals (i.e., length-12 ZAC sequence). In addition, sequencecontrolling section 116 identifies a correlation window corresponding toa resource on which the reference signals may be assigned (hereinafter,referred to as “reference signal resource”) in PUCCH resources that maybe used by terminal 200. Sequence control section 116 outputs theinformation indicating the correlation window corresponding to thereference signal resource on which the reference signals may be assignedin bundled ACK/NACK resources and the base sequence to correlationprocessing section 117-1. Sequence controlling section 116 outputs theinformation indicating the correlation window corresponding to thereference signal resource and the base sequence to correlationprocessing section 117-1. In addition, sequence controlling section 116outputs the information indicating the correlation window correspondingto the A/N resources on which an A/N and the reference signals for theA/N are assigned and the base sequence to correlation processing section117-2.

Despreading section 115-1 and correlation processing section 117-1perform processing on the reference signals extracted from the PUCCHregion corresponding to the bundled ACK/NACK resource.

To put it more specifically, despreading section 115-1 despreads thereference signal part using a Walsh sequence to be used insecondary-spreading for the reference signals of the bundled ACK/NACKresource by terminal 200 and outputs the despread signals to correlationprocessing section 117-1.

Correlation processing section 117-1 uses the information indicating thecorrelation window corresponding to the reference signal resource andthe base sequence and thereby finds a correlation value between thesignals received from despreading section 115-1 and the base sequencethat may be used in primary-spreading in terminal 200. Correlationprocessing section 117-1 outputs the correlation value to bundled A/Ndetermining section 121.

Despreading section 115-2 and correlation processing section 117-2perform processing on the reference signals and A/Ns extracted from theplurality of PUCCH regions corresponding to the plurality of A/Nresources.

To put it more specifically, despreading section 115-2 despreads thedata part and reference signal part using a Walsh sequence and a DFTsequence to be used in secondary-spreading for the data part andreference signal part of each of the A/N resources by terminal 200, andoutputs the despread signals to correlation processing section 117-2.

Correlation processing section 117-2 uses the information indicating thecorrelation window corresponding to each of the A/N resources and thebase sequence and thereby finds a correlation value between the signalsreceived from despreading section 115-2 and a base sequence that may beused in primary-spreading by terminal 200. Correlation processingsection 117-2 outputs each correlation value to A/N determining section118.

A/N determining section 118 determines, on the basis of the plurality ofcorrelation values received from correlation processing section 117-2,which of the A/N resources is used to transmit the signals from terminal200 or none of the A/N resources is used. When determining that thesignals are transmitted using one of the A/N resources from terminal200, A/N determining section 118 performs coherent detection using acomponent corresponding to the reference signals and a componentcorresponding to the A/N and outputs the result of coherent detection toretransmission control signal generating section 122. Meanwhile, whendetermining that terminal 200 uses none of the A/N resources, A/Ndetermining section 118 outputs the determination result indicating thatnone of the A/N resources is used to retransmission control signalgenerating section 122.

Bundled A/N despreading section 119 despreads, using a DFT sequence, thebundled ACK/NACK signals corresponding to the data part of the bundledACK/NACK resource received from PUCCH extracting section 114 and outputsthe despread signals to IDFT section 120.

IDFT section 120 transforms the bundled ACK/NACK signals in thefrequency-domain received from bundled A/N despreading section 119 intotime-domain signals by IDFT processing and outputs the bundled ACK/NACKsignals in the time-domain to bundled A/N determining section 121.

Bundled A/N determining section 121 demodulates the bundled ACK/NACKsignals corresponding to the data part of the bundled ACK/NACK resourcereceived from IDFT section 120, using the reference signal informationon the bundled ACK/NACK signals that is received from correlationprocessing section 117-1. In addition, bundled A/N determination section121 decodes the demodulated bundled ACK/NACK signals and outputs theresult of decoding to retransmission control signal generating section122 as the bundled A/N information. However, when the correlation valuereceived from correlation processing section 117-1 is smaller than athreshold, and bundled A/N determining section 121 thus determines thatterminal 200 does not use any bundled A/N resource to transmit thesignals, bundled A/N determining section 121 outputs the result ofdetermination to retransmission control signal generating section 122.

Retransmission control signal generating section 122 determines whetheror not to retransmit the data transmitted on the downlink componentcarrier (i.e., downlink data) on the basis of the information inputtedfrom bundled A/N determining section 121 and the information inputtedfrom A/N determining section 118 and generates retransmission controlsignals based on the result of determination. To put it morespecifically, when determining that downlink data transmitted on acertain downlink component carrier needs to be retransmitted,retransmission control signal generating section 122 generatesretransmission control signals indicating a retransmission command forthe downlink data and outputs the retransmission control signals to datatransmission controlling section 106. In addition, when determining thatthe downlink data transmitted on a certain downlink component carrierdoes not need to be retransmitted, retransmission control signalgenerating section 122 generates retransmission control signalsindicating not to retransmit the downlink data transmitted on thedownlink component carrier and outputs the retransmission controlsignals to data transmission controlling section 106. The details of themethod of grouping component carriers in retransmission control signalgenerating section 122 will be described, hereinafter.

(Configuration of Terminal)

FIG. 10 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1. In FIG. 10, terminal 200 includes radioreceiving section 201, CP removing section 202, fast Fourier transform(FFT) section 203, extraction section 204, demodulation section 205,decoding section 206, determination section 207, control section 208,demodulation section 209, decoding section 210, CRC section 211,response signal generating section 212, coding and modulation section213, primary-spreading sections 214-1 and 214-2, secondary-spreadingsections 215-1 and 215-2, DFT section 216, spreading section 217, IFFTsections 218-1, 218-2 and 218-3, CP adding sections 219-1, 219-2 and219-3, time-multiplexing section 220, selection section 221 and radiotransmitting section 222.

Radio receiving section 201 receives, via an antenna, OFDM signalstransmitted from base station 100 and performs reception processing suchas down-conversion, A/D conversion and/or the like on the received OFDMsignals. It should be noted that, the received OFDM signals includePDSCH signals assigned to a resource in a PDSCH (i.e., downlink data),or PDCCH signals assigned to a resource in a PDCCH.

CP removing section 202 removes a CP that has been added to the OFDMsignals from the OFDM signals that have undergone the receptionprocessing.

FFT section 203 transforms the received OFDM signals intofrequency-domain signals by FFT processing and outputs the resultantreceived signals to extraction section 204.

Extraction section 204 extracts, from the received signals to bereceived from FFT section 203, downlink control channel signals (i.e.,PDCCH signals) in accordance with coding rate information to bereceived. To put it more specifically, the number of CCEs (or R-CCEs)forming a downlink control information assignment resource variesdepending on the coding rate. Thus, extraction section 204 uses thenumber of CCEs that corresponds to the coding rate as units ofextraction processing, and extracts downlink control channel signals. Inaddition, the downlink control channel signals are extracted for eachdownlink component carrier. The extracted downlink control channelsignals are outputted to demodulation section 205.

Extraction section 204 extracts downlink data (i.e., downlink datachannel signals (i.e., PDSCH signals)) from the received signals on thebasis of information on the downlink data assignment resource intendedfor terminal 200 to be received from determination section 207 to bedescribed, hereinafter, and outputs the downlink data to demodulationsection 209. As described above, extraction section 204 receives thedownlink assignment control information (i.e., DCI) mapped to the PDCCHand receives the downlink data on the PDSCH.

Demodulation section 205 demodulates the downlink control channelsignals received from extraction section 204 and outputs the obtainedresult of demodulation to decoding section 206.

Decoding section 206 decodes the result of demodulation received fromdemodulation section 205 in accordance with the received coding rateinformation and outputs the obtained result of decoding to determinationsection 207.

Determination section 207 performs blind-determination (i.e.,monitoring) to find out whether or not the control information includedin the result of decoding received from decoding section 206 is thecontrol information intended for terminal 200. This determination ismade in units of decoding results corresponding to the units ofextraction processing. For example, determination section 207 demasksthe CRC bits by the terminal ID of terminal 200 and determines that thecontrol information resulted in CRC=OK (no error) as the controlinformation intended for terminal 200. Determination section 207 outputsinformation on the downlink data assignment resource intended forterminal 200, which is included in the control information intended forterminal 200, to extraction section 204.

In addition, when detecting the control information (i.e., downlinkassignment control information) intended for terminal 200, determinationsection 207 informs control section 208 that ACK/NACK signals will begenerated (or are present). Moreover, when detecting the controlinformation intended for terminal 200 from PDCCH signals, determinationsection 207 outputs information on a CCE that has been occupied by thePDCCH to control section 208.

Control section 208 identifies the A/N resource associated with the CCEon the basis of the information on the CCE received from determinationsection 207. Control section 208 outputs, to primary-spreading section214-1, a base sequence and a cyclic shift value corresponding to the A/Nresource associated with the CCE or the A/N resource previouslyindicated by base station 100, and also outputs a Walsh sequence and aDFT sequence corresponding to the A/N resource to secondary-spreadingsection 215-1. In addition, control section 208 outputs the frequencyresource information on the A/N resource to IFFT section 218-1.

When determining to transmit bundled ACK/NACK signals using a bundledACK/NACK resource, control section 208 outputs the base sequence andcyclic shift value corresponding to the reference signal part (i.e.,reference signal resource) of the bundled ACK/NACK resource previouslyindicated by base station 100 to primary-despreading section 214-2 andoutputs a Walsh sequence to secondary-despreading section 215-2. Inaddition, control section 208 outputs the frequency resource informationon the bundled ACK/NACK resource to IFFT section 218-2.

Control section 208 outputs a DFT sequence used for spreading the datapart of the bundled ACK/NACK resource to spreading section 217 andoutputs the frequency resource information on the bundled ACK/NACKresource to IFFT section 218-3.

Control section 208 selects the bundled ACK/NACK resource or the A/Nresource and instructs selection section 221 to output the selectedresource to radio transmitting section 222. Moreover, control section208 instructs response signal generating section 212 to generate thebundled ACK/NACK signals or the ACK/NACK signals in accordance with theselected resource.

Demodulation section 209 demodulates the downlink data received fromextraction section 204 and outputs the demodulated downlink data todecoding section 210.

Decoding section 210 decodes the downlink data received fromdemodulation section 209 and outputs the decoded downlink data to CRCsection 211.

CRC section 211 performs error detection on the decoded downlink datareceived from decoding section 210, for each downlink component carrierusing CRC and outputs an ACK when CRC=OK (no error) or outputs a NACKwhen CRC=Not OK (error) to response signal generating section 212.Moreover, CRC section 211 outputs the decoded downlink data as thereceived data when CRC=OK (no error).

Response signal generating section 212 generates response signals on thebasis of the reception condition of downlink data (i.e., result of errordetection on downlink data) on each downlink component carrier inputtedfrom CRC section 211 and information indicating a predetermined groupnumber. To put it more specifically, when instructed to generate thebundled ACK/NACK signals from control section 208, response signalgenerating section 212 generates the bundled ACK/NACK signals includingthe results of error detection for the respective component carriers asindividual pieces of data. Meanwhile, when instructed to generateACK/NACK signals from control section 208, response signal generatingsection 212 generates ACK/NACK signals of one symbol. Response signalgenerating section 212 outputs the generated response signals to codingand modulation section 213. The details of the method of groupingcomponent carriers in response signal generating section 212 will bedescribed, hereinafter.

Upon reception of the bundled ACK/NACK signals, coding and modulationsection 213 encodes and modulates the received bundled ACK/NACK signalsto generate the modulation signals of 12 symbols and outputs themodulation signals to DFT section 216. In addition, upon reception ofthe ACK/NACK signals of one symbol, coding and modulation section 213modulates the ACK/NACK signals and outputs the modulation signals toprimary-spreading section 214-1.

Primary-spreading sections 214-1 and 214-2 corresponding to the A/Nresources and reference signal resources of the bundled ACK/NACKresources spread the ACK/NACK signals or reference signals using thebase sequence corresponding to the resources in accordance with theinstruction from control section 208 and output the spread signals tosecondary-spreading sections 215-1 and 215-2.

Secondary-spreading sections 215-1 and 215-2 spread the receivedprimary-spread signals using a Walsh sequence or a DFT sequence inaccordance with an instruction from control section 208 and outputs thespread signals to IFFT sections 218-1 and 218-2.

DFT section 216 performs DFT processing on 12 time-series sets ofreceived bundled ACK/NACK signals to obtain 12 signal components in thefrequency-domain. DFT section 216 outputs the 12 signal components tospreading section 217.

Spreading section 217 spreads the 12 signal components received from DFTsection 216 using a DFT sequence indicated by control section 208 andoutputs the spread signal components to IFFT section 218-3.

IFFT sections 218-1, 218-2 and 218-3 perform IFFT processing on thereceived signals in association with the frequency positions where thesignals are to be allocated, in accordance with an instruction fromcontrol section 208. Accordingly, the signals inputted to IFFT sections218-1, 218-2 and 218-3 (i.e., ACK/NACK signals, the reference signals ofA/N resource, the reference signals of bundled ACK/NACK resource andbundled ACK/NACK signals) are transformed into time-domain signals.

CP adding sections 219-1, 219-2 and 219-3 add the same signals as thelast part of the signals obtained by IFFT processing to the beginning ofthe signals as a CP.

Time-multiplexing section 220 time-multiplexes the bundled ACK/NACKsignals received from CP adding section 219-3 (i.e., signals transmittedusing the data part of the bundled ACK/NACK resource) and the referencesignals of the bundled ACK/NACK resource to be received from CP addingsection 219-2 on the bundled ACK/NACK resource and outputs themultiplexed signals to selection section 221.

Selection section 221 selects one of the bundled ACK/NACK resourcereceived from time-multiplexing section 220 and the A/N resourcereceived from CP adding section 219-1 and outputs the signals assignedto the selected resource to radio transmitting section 222.

Radio transmitting section 222 performs transmission processing such asD/A conversion, amplification and up-conversion and/or the like on thesignals received from selection section 221 and transmits the resultantsignals to base station 100 via an antenna.

[Operations of Base Station 100 and Terminal 200]

Operations of base station 100 and terminal 200 having theabove-described configurations will be described.

In the present embodiment, terminal 200 groups component carriers foreach identical UL-DL configuration and reports results of errordetection corresponding to data received in a plurality of componentcarriers in each group using a specific one component carrier in thegroup.

FIG. 11 illustrates an example of a method of reporting results of errordetection in the present embodiment. In FIG. 11, terminal 200 isconfigured with four or more component carriers including componentcarriers of frequencies f₁, f₂, f_(A) and f_(B). In FIG. 11, thecomponent carrier of frequency f₁ is a PCell and the component carriersof f₂, f_(A) and f_(B) are SCells 1 to 3, respectively. In FIG. 11,Config 2 is set as a UL-DL configuration for the PCell and SCell 1 andConfig 3 is set as a UL-DL configuration for SCell 2 and SCell 3.

That is, in FIG. 11, the same UL-DL configuration (Config 2) is set forthe PCell and SCell 1 and the same UL-DL configuration (Config 3) is setfor SCell 2 and SCell 3.

Thus, response signal generating section 212 of terminal 200 putstogether the PCell and SCell 1 for which the same UL-DL configuration(Config 2) is set into one group (group 1) and puts together SCell 2 andSCell 3 for which the same UL-DL configuration (Config 3) is set intoone group (group 2).

Response signal generating section 212 generates one response signalindicating results of error detection of a plurality of componentcarriers in each group. For example, response signal generating section212 may perform spatial bundling and time-domain bundling on errordetection result bits of each component carrier in the group to generateone response signal as shown in FIG. 6.

Thus, in FIG. 11, one response signal is generated which reports resultsof error detection corresponding to the data signals respectivelyreceived in the PCell and SCell 1 in group 1. Furthermore, in FIG. 11,one response signal is generated which reports results of errordetection corresponding to the data signals respectively received inSCell 2 and SCell 3 in group 2.

Next, control section 208 selects one specific component carrier for onegroup as a component carrier to report the response signal generated ineach group. For example, as group 1 shown in FIG. 11, when a PCell isincluded in a group, control section 208 may always select the PCell asa specific component carrier to report a response signal. On the otherhand, as group 2 shown in FIG. 11, when no PCell is included in a group(when the group is formed of only SCells), control section 208 mayselect an SCell having a smallest index among SCells in the group as aspecific component carrier to report a response signal. That is, ingroup 2 shown in FIG. 11, SCell 2 is selected as the specific componentcarrier to report a response signal.

Thus, in FIG. 11, in group 1, the response signals indicating results oferror detection corresponding to all component carriers in group 1 arereported in UL subframes of the PCell. Furthermore, in group 2, theresponse signals indicating results of error detection corresponding toall component carriers in group 2 are reported in UL subframes of SCell2.

When base station 100 and terminal 200 have different recognition as towhich UL-DL configuration belongs to which group, the results of errordetection cannot be reported correctly. That is, it is necessary forbase station 100 and terminal 200 to have common recognition regarding agroup number indicating to which group (group 1 or 2 shown in FIG. 11)component carriers configured for terminal 200 belong. For this reason,base station 100 may previously set group numbers (not shown) forterminal 200.

Thus, response signal generating section 212 of terminal 200 generatesone response signal for each group on the basis of informationindicating previously set group numbers. On the other hand,retransmission control signal generating section 122 of base station 100identifies the group (component carrier) whose result of error detectioncorresponds to the result of coherent detection in A/N determiningsection 118 on the basis of the information indicating the group numberspreviously set in terminal 200 and determines whether or not toretransmit the data (downlink data) transmitted in each componentcarrier.

As described above, component carriers in which the same UL-DLconfiguration is set are grouped into one group as shown in FIG. 11.Therefore, timings of UL subframes and timings of DL subframes coincidewith each other among the component carriers in a group. Therefore, forexample, in group 1, even when, terminal 200 reports results of errordetection in SCell 1 shown in FIG. 11 using the PCell, the timing ofreporting the results of error detection in SCell 1 is the same as thetiming of reporting the results of error detection in the case of one CC(see FIG. 3).

That is, according to the present embodiment, the timing of reportingthe results of error detection of each component carrier configured forterminal 200 can always be kept at the same timing as the timing ofindication in the case of one CC shown in FIG. 3. That is, as shown inFIG. 7B, it is possible to prevent the timing of reporting the resultsof error detection from varying depending on the combination of UL-DLconfigurations set for terminal 200.

Furthermore, according to the present embodiment, a response signalindicating the results of error detection corresponding to the datasignal received in each component carrier in the group is indicated byone specific component carrier for each group. For this reason, it ispossible to suppress increases in the A/N resource amount and the amountof decoding processing on the results of error detection in base station100 compared to a case where results of error detection are reported foreach component carrier, independently (see FIG. 7A). In FIG. 11, group 1and group 2 are each formed of two component carriers, so that it ispossible to suppress to ½, the A/N resource amount and the amount ofdecoding processing on the results of error detection in base station100 compared to a case where results of error detection are reported foreach component carrier, independently (see FIG. 7A).

Here, it is assumed that a maximum of five component carriers (5 CCs)can be configured for one terminal 200. That is, there may be a casewhere five different UL-DL configurations are set respectively for fivecomponent carriers (5 CCs) for terminal 200. In this case, the fivecomponent carriers set for terminal 200 are grouped into five groups. Asdescribed above, terminal 200 reports results of error detection usingone component carrier for each group. Therefore, in this case, A/Nresources corresponding to a maximum of 5 CCs are necessary for terminal200. Moreover, base station 100 requires a maximum of 5-parallel (1group of results of error detection/1 parallel) decoding processing onresults of error detection.

However, when actual operation is taken into consideration, even whenfive component carriers are configured for one terminal 200, there isnot much need for increasing the degree of freedom of system settings toan extent that allows for setting of five different UL-DL configurationsfor component carriers. That is, the realistic number of UL-DLconfigurations capable of securing an appropriate degree of freedom ofsystem settings may be two to three types. In consideration of this, inthe present embodiment, even when a maximum of five component carriersare set for terminal 200, the five component carriers can be groupedinto two to three groups. Thus, even when a maximum of five componentcarriers are configured for terminal 200, only A/N resourcescorresponding to a maximum of two to three component carriers and 2- to3-parallel decoding processing on results of error detection in basestation 100 are necessary.

As described above, in the present embodiment, when ARQ is applied tocommunication using an uplink component carrier and a plurality ofdownlink component carriers associated with the uplink componentcarrier, and when a UL-DL configuration (ratio between UL subframes andDL subframes) set for each component carrier varies, it is possible toavoid a timing of reporting the results of error detection of the SCellfrom being changed from a timing of reporting the results of errordetection when only a single component carrier is configured, and alsoto suppress increases in the A/N resource amount used and the amount ofdecoding processing on the results of error detection in the basestation.

Embodiment 2

In the present embodiment, component carriers configured for terminal200 are grouped with attention focused on inclusion relations of ULsubframe timings between UL-DL configurations of respective componentcarriers set for terminal 200.

Hereinafter, the inclusion relation of UL subframe timings between UL-DLconfigurations will be described with reference to FIGS. 12A and 12B.Note that Configs 0 to 6 shown in FIGS. 12A and 12B respectivelycorrespond to Configs 0 to 6 shown in FIG. 3. That is, each UL-DLconfiguration shown in FIGS. 12A and 12B is a configuration pattern ofsubframes making up one frame (10 msec) and includes DL subframes and ULsubframes.

FIG. 12A is a diagram describing an inclusion relation between UL-DLconfigurations with attention focused on UL subframe timings amongtimings of DL subframes, UL subframes and special subframes of one frame(10 subframes; subframes #0 to #9). FIG. 12B is a diagram simplifyingthe description of FIG. 12A and with attention focused only on theinclusion relation.

In FIG. 12A, for example, in Config 0, subframes #2, #3, #4, #7, #8 and#9 correspond to UL subframes, and the proportion of UL subframes inConfig 0 is highest in one frame among all UL-DL configurations (Configs0 to 6).

In FIG. 12A, for example, in Config 6, subframes #2, #3, #4, #7 and #8correspond to UL subframes.

Here, as shown in FIG. 12A, subframe #2, #3, #4, #7 and #8 correspond toUL subframes in both Config 0 and Config 6. It can also be said thatConfig 6 is equivalent to Config 0 with subframe #9 assigned as a DLsubframe, and Config 0 is equivalent to Config 6 with subframe #9assigned as a UL subframe.

That is, timings of UL subframes in Config 6 constitute a subset oftimings of UL subframes in Config 0. That is, UL subframe timings ofConfig 6 are included in UL subframe timings of Config 0. Such arelation (inclusion relation) between a set (Config 0) and a subset(Config 6) exists in all two UL-DL configurations except threecombinations between Config 1 and Config 3, Config 2 and Config 4 andConfig 3 and Config 2 as shown in FIG. 12A and FIG. 12B.

In FIG. 12A and FIG. 12B, among UL-DL configurations having inclusionrelations regarding UL subframes, UL-DL configurations having more ULsubframes are called “high-order UL-DL configurations” and UL-DLconfigurations having fewer UL subframes are called “low-order UL-DLconfigurations.” That is, in FIG. 12B, Config 0 is a highest-order UL-DLconfiguration and Config 5 is a lowest-order UL-DL configuration.

That is, according to FIG. 12A, in a high-order UL-DL configuration, ULsubframes are set at least at the same timings as those of UL subframesset in a low-order UL-DL configuration.

Thus, in the present embodiment, among a plurality of component carriersconfigured for terminal 200, terminal 200 groups component carriershaving an inclusion relation among UL subframe timings into one group.In addition, in each group, terminal 200 reports response signalsindicating results of error detection of a plurality of componentcarriers in a group using a component carrier in which a highest-orderUL-DL configuration is set in the inclusion relations of UL subframetimings.

FIG. 13A illustrates a method of grouping component carriers on thebasis of the inclusion relations of UL subframe timings shown in FIGS.12A and 12B. In FIG. 13A, four component carriers are configured forterminal 200. Moreover, Config 2, Config 5, Config 3 and Config 4 areset respectively for the four component carriers shown in FIG. 13A.

As shown in FIG. 13B, in the inclusion relations of UL subframe timings,Config 2 includes Config 5 and Config 3 includes Config 4. Thus, asshown in FIG. 13A, response signal generating section 212 of terminal200 groups the component carrier in which Config 2 is set and thecomponent carrier in which Config 5 is set as group 1, and groups thecomponent carrier in which Config 3 is set and the component carrier inwhich Config 4 is set as group 2.

Next, control section 208 selects a component carrier in which Config 2including UL subframe timings as the highest-order configuration ingroup 1 is set as a specific component carrier to report responsesignals indicating results of error detection of the component carriersin group 1. Similarly, control section 208 selects a component carrierin which Config 3 including UL subframe timings as the highest-orderconfiguration in group 2 is set as a specific component carrier toreport response signals indicating results of error detection of thecomponent carriers in group 2. Consequently, in FIG. 13A, results oferror detection of all component carriers in group 1 are reported by thecomponent carrier in which Config 2 is set and results of errordetection of all component carriers in group 2 are reported by thecomponent carrier in which Config 3 is set.

To be more specific, as shown in FIG. 13A, subframes #2 and #7 in Config2 correspond to UL subframes and subframe #2 in Config 5 corresponds toa UL subframe. Thus, terminal 200 (control section 208) reports oneresponse signal indicating the results of error detection of thecomponent carrier in which Config 2 is set and the results of errordetection of the component carrier in which Config 5 is set usingsubframe #2 which has the same UL subframe timing as the UL subframetiming of the component carrier in which Config 5 is set in thecomponent carrier in which Config 2 in group 1 shown in FIG. 13A is set.Thus, the results of error detection of the component carrier in whichConfig 5 is set is reported by the same UL subframe (subframe #2) asthat in the case of one CC (see FIG. 3, i.e., 3GPP Release 8 or 10) asshown in FIG. 13A. The same applies to group 2 shown in FIG. 13A.

On the other hand, terminal 200 reports only the results of errordetection of the component carrier in which Config 2 is set usingsubframe #7 (DL subframe in Config 5) of the component carrier in whichConfig 2 in group 1 shown in FIG. 13A is set.

That is, even when the results of error detection of the componentcarrier in the same group are transmitted using a specific componentcarrier, the timing of reporting the results of error detection of eachcomponent carrier in the group can be kept at the same timing as that inthe case of one CC (see FIG. 3).

In contrast, as shown in FIG. 13B, regarding the inclusion relations ofUL subframe timings, there is no inclusion relation between Config 2 andConfig 3. That is, Config 2 and Config 3 include UL subframes (subframe#7 of Config 2, subframes #3 and #4 of Config 3) set at least differenttimings. In FIG. 13A, control section 208 transmits response signalsincluding results of error detection corresponding to data signalsreceived in the component carrier in which Config 3 is set using thecomponent carrier in which Config 3 is set. That is, the results oferror detection of the component carrier in which Config 3 having noinclusion relation with Config 2 which is the highest-order UL-DLconfiguration in group 1 is set are transmitted using component carriersof any group other than group 1 including the component carrier in whichConfig 2 is set. This makes it possible to keep the timings of reportingthe results of error detection of the component carrier in which Config3 is set to the same timing in the case of one CC (see FIG. 3).

Thus, terminal 200 groups component carriers configured for terminal 200on the basis of inclusion relations of UL subframe timings. Even whendifferent UL-DL configurations are set for terminal 200, it is therebypossible to maintain the timing of reporting the results of errordetection of each component carrier to the same timing as that in thecase of one CC (see FIG. 3).

(Number of Groups and PCell Setting Method)

Next, a description will be given of the minimum necessary number ofgroups in the aforementioned grouping method and the PCell settingmethod when component carriers (CCs) for terminal 200 are reset (added).

FIGS. 14A to 14C are diagrams provided for describing a case where aPCell is reset when a component carrier (CC) for terminal 200 is newlyadded (FIG. 14A) and cases where the PCell is not reset (FIGS. 14B and14C). As to the cases where the PCell is not reset, further details willbe given about a case where results of error detection need not alwaysbe reported from the PCell (FIG. 14B) and a case where the results oferror detection is always reported from the PCell (FIG. 14C).

In FIGS. 14A to 14C, only one component carrier of Config 2 isconfigured for terminal 200 before resetting component carriers, and thecomponent carrier (that is, PCell) is assumed to be group 1 and theresults of error detection are reported from the PCell (upper rows inFIGS. 14A to 14C). In FIGS. 14A to 14C, two component carriers (CCs) ofConfig 1 and Config 3 are newly added to terminal 200 (lower rows inFIGS. 14A to 14C). Here, Config 1 includes UL subframe timing of Config2 which is the PCell before the CC is added. On the other hand, Config 3has no inclusion relation with UL subframe timings of Config 2 which isthe PCell before the CC is added.

In FIG. 14A (when the PCell is reset), when two component carriers ofConfig 1 and Config 3 are added, the component carrier of Config 2 whichis the current PCell is no longer the “highest-order component carrierin which a UL-DL configuration including UL subframe timings is set.”For this reason, the “component carrier in which the highest UL-DLconfiguration including UL subframe timings is set” is reset to thePCell. That is, as shown in FIG. 14A, the newly set component carrier ofConfig 1 is reset to the PCell. In FIG. 14A, the newly set componentcarrier of Config 3 may also be reset to the PCell.

In FIG. 14A, Config 1 and Config 2 which have an inclusion relationregarding UL subframe timings are grouped as same group 1. The responsesignals indicating results of error detection corresponding to bothcomponent carriers of Config 1 and Config 2 are reported by thehighest-order component carrier in group 1 in which Config 1 includingUL subframe timings is set. Furthermore, in FIG. 14A, response signalsindicating the results of error detection corresponding to the componentcarrier of Config 3 are reported by the component carrier (group 2) inwhich Config 3 is set.

In FIG. 14B (the case where the PCell is not reset and the case wherethe results of error detection need not always be reported from thePCell), when the two component carriers of Config 1 and Config 3 areadded, the current PCell is no longer the “highest-order componentcarrier in which a UL-DL configuration including UL subframe timings isset.” However, in FIG. 14B, since results of error detection need notalways be reported from the PCell, the component carrier of Config 2 mayremain to be set to the PCell. That is, in FIG. 14B, the grouping methodand the component carrier whereby response signals in the group arereported are the same as those in FIG. 14A, whereas the componentcarrier set to the PCell is different from that in FIG. 14A. That is, ingroup 1 shown in FIG. 14B, the UL-DL configuration (Config 1) forreporting a response signal (results of error detection) may bedifferent from the UL-DL configuration (Config 2) of the componentcarrier set in the PCell.

FIG. 14C illustrates a case where the PCell is not reset and a casewhere the results of error detection are always reported from the PCell.In order for the results of error detection to be always reported by thePCell, the PCell needs to be the “highest-order component carrier inwhich a UL-DL configuration including UL subframe timings is set.”

In order for the component carrier of Config 2 which is the currentPCell to continue to be the “highest-order component carrier in which aUL-DL configuration including UL subframe timings is set” even when twocomponent carriers of Config 1 and Config 3 shown in FIG. 14C are added,the UL-DL configuration that can belong to the same group needs to beConfig 5 (or Config 2). That is, the component carrier that can belongto the same group as that of the PCell needs to be a component carrierin which a UL-DL configuration identical to the UL-DL configuration setin the PCell is set or a component carrier in which a UL-DLconfiguration set in the PCell is the UL-DL configuration (that is, alower-order UL-DL configuration) including UL subframe timings.

In contrast, in FIG. 14C, component carriers newly added to terminal 200are component carriers of Config 1 and Config 3. That is, in FIG. 14C,component carriers newly added to terminal 200 are component carriers inwhich a high-order UL-DL configuration is set with respect to the PCell(Config 2). For this reason, these component carriers cannot belong togroup 1 to which the PCell belongs. Moreover, no inclusion relation ofUL subframe timings exists between Config 1 and Config 3. For thisreason, these component carriers cannot belong to the same group.

As a result, in FIG. 14C, the component carriers set for terminal 200are grouped so as to form their respective groups (groups 1 to 3). Ineach of groups 1 to 3, response signals (results of error detection) arereported by the “highest-order component carrier in which a UL-DLconfiguration including UL subframe timings is set.” That is, theresults of error detection are reported by the component carrier (PCell)of Config 2 in group 1 shown in FIG. 14C, the results of error detectionare reported by the component carrier of Config 3 in group 2 and theresults of error detection are reported by the component carrier ofConfig 1 in group 3.

The following is the minimum necessary number of groups to support allcombinations of UL-DL configurations when component carriers are groupedon the basis of inclusion relations of UL subframe timings, and theresults of error detection are reported using the highest-ordercomponent carrier in which a UL-DL configuration including UL subframetimings is set for each group. That is, as shown in FIG. 14A, when thePCell is reset as the “highest-order component carrier in which a UL-DLconfiguration including UL subframe timings is set,” the minimumnecessary number of groups is two. Furthermore, as shown in FIG. 14B, inthe case where the PCell is not reset and in the case where results oferror detection need not always be reported from the PCell, the minimumnecessary number of groups is two. Furthermore, as shown in FIG. 14C, inthe case where the PCell is not reset and in the case where results oferror detection are always reported from the PCell, the minimumnecessary number of groups is three.

In other words, in the present embodiment, Configs 0 to 6 are groupedinto a maximum of two or three groups in accordance with the method ofreporting response signals (results of error detection).

The grouping method and the method of reporting results of errordetection when the PCell is reset and when the PCell is not reset havebeen described in detail with reference to FIG. 14. It is also possibleto implement a setting that makes it possible to select whether or notto reset the PCell or to select whether or not to always report resultsof error detection from the PCell in the case where the PCell is notreset.

(Signaling Method)

Next, the method of indicating a group of component carriers configuredfor terminal 200 (signaling method) will be described.

When component carriers are grouped, the groups are referred to as group1 and group 2 in FIGS. 13A and 13B and FIGS. 14A to 14C. However, as inthe case of Embodiment 1, unless base station 100 and terminal 200 sharethe same recognition as to which UL-DL configuration belongs to whichgroup, results of error detection cannot be reported correctly. That is,it is necessary for base station 100 and terminal 200 to have commonrecognition regarding a group number indicating to which group acomponent carrier configured for terminal 200 belongs. For this reason,base station 100 needs to previously set group numbers for terminal 200.

Thus, the group number setting method and the signaling method will bedescribed in detail with reference to FIGS. 15A and 15B and FIG. 16.Hereinafter, each one of group number setting methods 1 to 4 will bedescribed.

<Setting Method 1>

Setting method 1 is a method whereby group numbers are set respectivelyfor the UL-DL configurations. That is, according to setting method 1, agroup number is set for each UL-DL configuration and 1 bit per UL-DLconfiguration is indicated (1 bit/1 Config).

An example of setting method 1 is a method as shown in FIG. 15A whereby1 bit (maximum number of groups is two) or 2 bits (maximum number ofgroups is three or four) per UL-DL configuration is indicated (method1-1). In FIG. 15A, group number ‘1’ is indicated for Configs 0 to 2, 5and 6 and group number ‘2’ is indicated for Configs 3 and 4.

On the other hand, another example of setting method 1 is a method asshown in FIG. 15B whereby a plurality of correspondence tables areprovided in which UL-DL configurations and group numbers are previouslyset and a number indicating which correspondence table should be used(correspondence table number) is indicated (methods 1 and 2).

Furthermore, a further example of setting method 1 is a method wherebygroup numbers are fixedly set for the respective UL-DL configurations(methods 1 to 3). In this case, signaling for indicating group numbersfrom base station 100 to terminal 200 is unnecessary.

In setting method 1, since group numbers are set for the respectiveUL-DL configurations, the same UL-DL configuration cannot be set amongdifferent groups.

<Setting Method 2>

Setting method 2 is a method whereby a group number is set for eachcomponent carrier configured for terminal 200. That is, in settingmethod 2, a group number is set for each component carrier and 1 bit percomponent carrier is indicated (1 bit/1 CC).

For example, as shown in FIG. 16, terminal A groups component carriersin which Configs. 1, 2, 3, 4 and 6 are set into one group. That is,group number ‘1’ is set for each of the component carriers in whichConfigs. 1, 2, 3, 4 and 6 are set. Furthermore, as shown in FIG. 16,terminal B groups component carriers in which Configs 1 and 2 are set asgroup 1 and groups component carriers in which Config 3 and 4 are set asgroup 2. That is, group number ‘1’ is set for the component carriers inwhich Configs 1 and 2 are set and group number ‘2’ is set for thecomponent carriers in which Configs 3 and 4 are set.

That is, since base station 100 needs to indicate group numbers set forthe component carriers to each terminal 200, the number of bits forsignaling increases compared to setting method 1. However, there is nosetting limitation illustrated in setting method 1. That is, settingmethod 2 allows the same UL-DL configuration to be set even amongdifferent groups. That is, the same UL-DL configuration can belong togroup 1 or belong to group 2 depending on the terminal.

Setting method 2 can further be subdivided into a method (method 2-1)whereby a group number is set for each component carrier configured forterminal 200 and a method (method 2-2) whereby a component carrier forreporting results of error detection is set for each terminal 200. Inmethod 2-2, only a component carrier for reporting results of errordetection is indicated to terminal 200. Thus, it is necessary topreviously set whether to determine fixedly or changeably by a setting,between base station 100 and terminal 200, which component carrierbelongs to the same group as the component carrier to be indicated.

<Setting Method 3>

Setting method 3 is a method of indicating only switching between ON/OFF(whether or not to perform grouping) for each terminal 200. That is, insetting method 3, only 1 bit is indicated. Between base station 100 andterminal 200, setting method 3 may be singly set or setting method 3 maybe set in combination with method 1 or setting method 2.

<Setting Method 4>

Setting method 4 is a method whereby only one group is always set foreach terminal 200. In setting method 4, such a limitation is providedthat a UL-DL configuration that cannot be included in a componentcarrier of the highest-order UL-DL configuration including UL subframetimings should not be set.

Group number setting methods 1 to 4 have been described so far.

In this way, in the present embodiment, response signal generatingsection 212 in terminal 200 groups the first component carrier and thesecond component carrier. Here, in the UL-DL configuration set in thefirst component carrier, UL subframes are set at the same timings asthose of UL subframes of the UL-DL configuration set in at least theabove second component carrier. Control section 208 transmits a responsesignal including results of error detection corresponding to datasignals respectively received in the first component carrier and thesecond component carrier using the first component carrier. To be morespecific, control section 208 transmits the above-described one responsesignal using a UL subframe in the first component carrier which has thesame timing as that of UL subframe of the UL-DL configuration set in thesecond component carrier.

Even when terminal 200 reports results of error detection of allcomponent carriers in a group using a specific component carrier in thegroup (component carrier in which the highest-order UL-DL configurationin the group including UL subframe timings is set), it is therebypossible to maintain the timing of reporting results of error detectionof other component carriers to be the same as the timing of reportingthe results of error detection in the case of one CC. That is, thepresent embodiment can prevent, as shown in FIG. 7B, the timing ofreporting the results of error detection from varying depending on thecombination of UL-DL configurations set for terminal 200.

Furthermore, according to the present embodiment, Configs 0 to 6 aregrouped into a maximum of two or three groups as shown in FIGS. 14A to14C. That is, it is possible to suppress the A/N resource amount and theamount of decoding processing on results of error detection in basestation 100 to a maximum of two- or three-fold increase irrespective ofthe number of component carriers configured for terminal 200 compared tothe case where results of error detection are reported independently foreach component carrier (see FIG. 7A).

By so doing, when ARQ is applied to communication using an uplinkcomponent carrier and a plurality of downlink component carriersassociated with the uplink component carrier and when a UL-DLconfiguration (ratio between UL subframes and DL subframes) to be setvaries for each component carrier, the present embodiment can preventthe timing of reporting the results of error detection of the SCell fromchanging from the timing of reporting the results of error detectionwhen only a single component carrier is set and suppress increases inthe A/N resource amount used and the amount of decoding processing onresults of error detection in the base station.

In the present embodiment, it is possible to employ a method thatdeactivates all component carriers of a group upon deactivation of acomponent carrier for reporting results of error detection in the group.Alternatively, it is possible to employ a method that does not allow fordeactivation (that is, preventing deactivation) of the component carrierfor reporting results of error detection in each group.

Furthermore, in the present embodiment, the maximum number of groupscorresponding to component carriers configured for terminal 200 may beset for each terminal 200. For example, the maximum number of groups maybe set to one for a low-end terminal and the maximum number of groupsmay be set to two for a high-end terminal. Moreover, an upper limitvalue of the number of groups is equal to the number of configuredcomponent carriers. Adopting the number of groups greater than theminimum necessary number of groups to support all the aforementionedcombinations of UL-DL configurations causes the number of bits ofresults of error detection reported per component carrier to increase,and thus can prevent the estimation accuracy of results of errordetection in the base station from decreasing.

Furthermore, in the present embodiment, the method of grouping componentcarriers is not limited to the example shown in FIGS. 13A and 13B. Forexample, in the UL-DL configuration shown in FIG. 12B, Config 3, Config4 and Config 5 may be grouped as group 1, and only Config 2 may begrouped as group 2.

In FIG. 12B, when a higher-order UL-DL configuration including ULsubframe timings (e.g., Config 1, Config 6 or Config 0) is set incomponent carriers in common to Config 2 and Config 4 which have noinclusion relation, the UL-DL configuration, Config 2 and Config 4 maybe grouped as the same group.

Furthermore, in the UL-DL configuration shown in FIG. 12B, Config 3 andConfig 5 may be grouped as group 1, Config 2 may be grouped as group 2and Config 4 may be grouped as group 3. That is, as the inclusionrelation shown in FIG. 12B, not mutually neighboring UL-DLconfigurations (e.g., Config 3 and Config 5) may also be grouped as thesame group.

That is, terminal 200 may perform grouping so as to prevent groups frombeing formed only of combinations of UL-DL configurations mutuallyhaving no inclusion relation among UL subframe timings (in FIG. 12B,Config 1 and Config 3, Config 2 and Config 3, and Config 2 and Config4). Alternatively, terminal 200 may also perform grouping so as toprevent groups from being formed of combinations of UL-DL configurationsmutually having no inclusion relation among UL subframe timings andlower UL-DL configurations including UL subframe timings than the UL-DLconfigurations making up the combinations (in FIG. 12B, Config 2, Config4 or Config 5 for the combination of Config 1 and Config 3, Config 4 orConfig 5 for the combination of Config 2 and Config 3, and Config 5 forthe combination of Config 2 and Config 4).

In short, terminal 200 can group a combination of UL-DL configurationsmutually having no inclusion relation among UL subframe timings onlyinto a group to which a higher-order UL-DL configuration including bothof the two UL-DL configurations making up the combination belongs (inFIG. 12B, Config 0 or Config 6 for the combination of Config 1 andConfig 3, Config 0 or Config 6 for the combination of Config 2 andConfig 3, Config 0, Config 6 or Config 1 for the combination of Config 2and Config 4).

Moreover, there can also be a case where there are a plurality ofcomponent carriers in which a highest-order UL-DL configurationincluding UL subframe timings is set in the same group. That is, therecan also be a case where there are a plurality of component carriers inwhich the same highest-order UL-DL configuration including UL subframetimings is set. In this case, when one of the component carriers inwhich the same UL-DL configuration is set is a PCell in the group, thePCell may be configured as the component carrier for reporting resultsof error detection. On the other hand, when there is no PCell in thegroup (when the group is only formed of SCells), an SCell having asmaller SCell index may be configured as the component carrier forreporting results of error detection. However, even in the case of agroup to which a PCell belongs, results of error detection need notalways be reported from the PCell. The component carrier for reportingresults of error detection is a “component carrier in which ahighest-order UL-DL configuration including UL subframe timings is set”in each group. When the PCell is not a “component carrier in which ahighest-order UL-DL configuration including UL subframe timings is set,”the PCell may be reconfigured as a “component carrier in which ahighest-order UL-DL configuration including UL subframe timings is set.”

(Guideline for Grouping)

As described above, the method of grouping component carriers is notlimited to one method. For example, in FIG. 13, Config 3, Config 4 andConfig 5 may be grouped as group 1 and only Config 2 may be grouped asgroup 2. Thus, a guideline for determining the grouping method will bedescribed, hereinafter.

An example of a guideline for grouping is a method whereby grouping isperformed in such a way that the number of bits of results of errordetection becomes uniform among groups. Another guideline for groupingis a method whereby grouping is performed in such a way that the numberof component carriers becomes uniform among groups. A further guidelinefor grouping is a method whereby grouping is performed in such a waythat the number of bits of results of error detection becomes uniformamong groups with also MIMO and non-MIMO configurations taken intoconsideration. These guidelines allow energy per bit of results of errordetection to be smoothed.

Furthermore, there is a method whereby grouping is performed so as toavoid grouping of UL-DL configurations of 10-msec cycle (e.g., Config 3,4 and 5) or UL-DL configurations having a high DL subframe ratio. Thismethod can prevent the number of bits of results of error detection tobe reported per group from increasing.

Furthermore, grouping may also be adopted so that the number ofcomponent carriers per group is two or fewer. This method allows channelselection which is a method of reporting results of error detection thatsupports only indication of results of error detection for a maximum oftwo component carriers to be applied to each group. Note that it mayalso be possible to adopt different methods of reporting results oferror detection among groups (channel selection or DFT-S-OFDM). Whetherto use channel selection or DFT-S-OFDM may be configurable for eachgroup. Furthermore, the method of reporting results of error detectionmay be changeable in the group for every subframe on the basis of, forexample, the number of bits of results of error detection beforebundling and the number of component carriers to which downlink dataassociated with the results of error detection to be reported isassigned. For example, in FIG. 13, in group 1, component carriers towhich downlink data associated with results of error detection to bereported is assigned are both component carriers of Configs 2 and 5 insubframe #2 and only the component carrier of Config 2 in subframe #7.Thus, in group 1 shown in FIG. 13, the method of reporting results oferror detection may be changeable between subframe #2 and subframe #7.

Embodiment 3

In LTE-Advanced, cross-carrier scheduling may be applied in which aPDCCH of a PCell indicates a PDSCH of a component carrier (SCell) otherthan the PCell. That is, in cross-carrier scheduling, the PCell is a“cross-carrier scheduling source (controlling side)” and the SCell is a“cross-carrier scheduling destination (controlled side).”

When UL-DL configurations differ among a plurality of componentcarriers, cross-carrier scheduling can be performed under the followingconditions. That is, when a component carrier of a cross-carrierscheduling destination is a DL subframe or a special subframe, acomponent carrier of a cross-carrier scheduling source is a DL subframeor special subframe. That is, when a region (PDSCH) for indicatingdownlink data exists in a component carrier of the cross-carrierscheduling destination, there needs to be a region (PDCCH) forindicating a downlink control signal so as to indicate the downlink datain the component carrier of the cross-carrier scheduling source.

On the other hand, when the component carrier of the cross-carrierscheduling destination is a UL subframe, there is no need to indicate aPDSCH for the component carrier of the cross-carrier schedulingdestination. Therefore, the component carrier of the cross-carrierscheduling source may be any one of a UL subframe, DL subframe andspecial subframe.

FIGS. 17A and 17B illustrate an example of a case where cross-carrierscheduling is performed. FIG. 17A is an example of a case whereintra-group cross-carrier scheduling is performed. FIG. 17B is anexample of a case where inter-group cross-carrier scheduling isperformed.

FIG. 17A illustrates a case where cross-carrier scheduling is performedfrom a component carrier (PCell) in which Config 3 is set to a componentcarrier in which Config 4 is set. As shown in FIG. 17A, when subframesin both component carriers become DL subframes, cross-carrier schedulingcan be performed since there can be a PDCCH which is a cross-carrierscheduling source and a PDSCH which is a cross-carrier schedulingdestination. On the other hand, in subframe #4 shown in FIG. 17A, asubframe in the component carrier (Config 3) which is a cross-carrierscheduling source becomes a UL subframe and a subframe in the componentcarrier (Config 4) which is a cross-carrier scheduling destinationbecomes a DL subframe. Therefore, there can be a PDSCH in thecross-carrier scheduling destination, but a PDCCH in the cross-carrierscheduling source cannot be assigned and it is impossible to performcross-carrier scheduling.

On the other hand, FIG. 17B illustrates a case where a component carrierin which Config 3 is set and a component carrier in which Config 4 isset exist in group 1, and a component carrier in which Config 2 is setand a component carrier in which Config 5 is set exist in group 2. Asshown in FIG. 17B, subframes #3 and #4 of a component carrier (Config 3)in group 1 which is a cross-carrier scheduling source become ULsubframes, and those in component carriers (Configs 2 and 5) in group 2which are cross-carrier scheduling destinations become DL subframes.Therefore, although there can be a PDSCH in the cross-carrier schedulingdestination, since a PDCCH which becomes a cross-carrier schedulingsource cannot be assigned, cross-carrier scheduling cannot be performed.

In the present embodiment, component carriers configured for terminal200 are grouped with attention focused on inclusion relations of DLsubframe timings among UL-DL configurations when performingcross-carrier scheduling.

Hereinafter, the inclusion relations of DL subframe timings among UL-DLconfigurations will be described with reference to FIGS. 18A and 18B.Note that Configs 0 to 6 shown in FIGS. 18A and 18B respectivelycorrespond to Configs 0 to 6 shown in FIG. 3.

FIG. 18A is provided for describing inclusion relations among UL-DLconfigurations with attention focused on DL subframe timings amongtimings of DL subframes, UL subframes and special subframescorresponding to one frame (10 subframes; subframes #0 to #9). FIG. 18Bis provided for describing FIG. 18A with attention focused only on theinclusion relations, by simplifying the illustration of FIG. 18A.

In FIG. 18A, for example, subframes #0, and #3 to #9 in Config 5 becomeDL subframes, and the proportion of DL subframes per frame in Config 5is highest among all UL-DL configurations (Configs 0 to 6).

In FIG. 18A, for example, subframes #0, and #4 to #9 in Config 4 becomeDL subframes.

Here, as shown in FIG. 18A, subframes #0, and #4 to #9 are DL subframesin both Config 5 and Config 4. Furthermore, it can also be said thatConfig 4 is equivalent to Config 5 with subframe #3 replaced by a ULsubframe or Config 5 is equivalent to Config 4 with subframe #3 replacedby a DL subframe.

That is, DL subframe timings in Config 4 are a subset of DL subframetimings in Config 5. That is, the DL subframe timings in Config 4 areincluded in the DL subframe timings in Config 5. Such a relation(inclusion relation) between a set (Config 5) and a subset (Config 4)exists between all two UL-DL configurations except three combinations ofConfig 1 and Config 3, Config 2 and Config 4, and Config 3 and Config 2as shown in FIG. 18A and FIG. 18B.

Note that in FIG. 18A and FIG. 18B, among UL-DL configurations havinginclusion relations regarding DL subframes, a UL-DL configuration havingmore DL subframes is called “high-order UL-DL configuration” and a UL-DLconfiguration having fewer DL subframes is called “low-order UL-DLconfiguration.” That is, in FIG. 18B, Config 5 is the highest-orderUL-DL configuration and Config 0 is the lowest-order UL-DLconfiguration. That is, the inclusion relations of DL subframe timingsshown in FIG. 18A and FIG. 18B are diametrically opposite to theinclusion relations of UL subframe timings shown in FIG. 12A and FIG.12B.

According to FIG. 18A, in a high-order UL-DL configuration, a DLsubframe is set at least at the same timing as that of a DL subframe setin a low-order UL-DL configuration. That is, a UL subframe is never setin a high-order UL-DL configuration at the same timing as that of a DLsubframe set in a low-order UL-DL configuration.

Thus, the present embodiment gives a condition that a component carrierwhich becomes a cross-carrier scheduling source in a group (intra-group)is a component carrier in which a “highest-order” UL-DL configurationincluding “DL” subframe timings in each group is set. In other words, acomponent carrier which becomes a cross-carrier scheduling source in agroup (intra-group) can also be expressed in each group as a componentcarrier in which a “lowest-order” UL-DL configuration including “UL”subframe timings is set.

On the other hand, the present embodiment gives a condition that acomponent carrier which becomes a cross-carrier scheduling source amonggroups (inter-group) is a component carrier in which a highest-orderUL-DL configuration including DL subframe timings in all groups is set.

FIGS. 19A to 19C illustrate a more specific example of a cross-carrierscheduling method in the case where grouping focused on the inclusionrelations shown in FIGS. 18A and 18B is performed.

In FIG. 19A, grouping is performed in such a way that component carriersin which Configs 3 and 4 are respectively set are grouped as group 1 andcomponent carriers in which Configs 2 and 5 are respectively set aregrouped as group 2. FIG. 19B illustrates (intra-group) cross-carrierscheduling in group 1 and FIG. 19C illustrates (inter-group)cross-carrier scheduling between groups.

As shown in FIG. 19A, in inclusion relations of DL subframe timingsamong UL-DL configurations, Config 4 is a higher-order UL-DLconfiguration than Config 3. Thus, in FIG. 19B, the component carrier inwhich Config 4 is set becomes a cross-carrier scheduling source and thecomponent carrier in which Config 3 is set becomes a cross-carrierscheduling destination. In this way, as shown in FIG. 19B, at the sametiming as that of a DL subframe set in the component carrier of thecross-carrier scheduling destination (subframe in which a PDSCH exists),even the cross-carrier scheduling source always becomes the DL subframe(subframe in which a PDCCH exists). Furthermore, as shown in FIG. 19B,in subframe #4, since the component carrier (Config 3) of thecross-carrier scheduling destination is a UL subframe, cross-carrierscheduling need not be performed.

Similarly, as shown in FIG. 19A, in the inclusion relations of DLsubframe timings among UL-DL configurations, Config 5 is a higher-orderUL-DL configuration than Configs 2 to 4. Thus, in FIG. 19C, thecomponent carrier in which Config 5 is set becomes a cross-carrierscheduling source and the component carriers in which Configs 2 to 4 areset become cross-carrier scheduling destinations. Thus, as shown in FIG.19C, just like FIG. 19B, at the same timing as that of a DL subframe setin the component carrier of the cross-carrier scheduling destination(subframe in which a PDSCH exists), even the cross-carrier schedulingsource always becomes a DL subframe (subframe in which a PDCCH exists).Furthermore, as shown in FIG. 19C, just like FIG. 19B, since thecomponent carrier of the cross-carrier scheduling destination (Config 3or 4) is a UL subframe in subframe #3 and subframe #4, cross-carrierscheduling need not be performed.

That is, according to the present embodiment, as shown in FIG. 19B andFIG. 19C, there is no such subframe on which cross-carrier schedulingcannot be performed as shown in FIG. 17B. That is, cross-carrierscheduling can be performed on any subframes shown in FIG. 19B and FIG.19C.

Furthermore, according to the present embodiment, in the inclusionrelations of DL subframe timings among UL-DL configurations, a componentcarrier in which a high-order UL-DL configuration is set is configuredas a cross-carrier scheduling source. In other words, a componentcarrier in which a UL-DL configuration having a higher proportion of DLsubframes is set is configured as a cross-carrier scheduling source.Thus, during cross-carrier scheduling, the possibility of a PDCCHbecoming insufficient decreases even when a PDCCH indicating a PDSCH ofanother component carrier is assigned in the component carrier.

(Signaling Method)

Next, the method of indicating (method of signaling) groups of componentcarriers configured for terminal 200 will be described.

In FIGS. 19A, 19B, and 19C, groups resulting from grouping of componentcarriers are described as group 1, group 2, and so forth. However, as inthe case of Embodiment 2, when base station 100 and terminal 200 havedifferent recognition as to which UL-DL configuration belongs to whichgroup, PDSCH assignment by a PDCCH cannot be correctly indicated. Thatis, it is necessary for base station 100 and terminal 200 to have commonrecognition as to group numbers indicating to which group componentcarriers set for terminal 200 belong. For this reason, base station 100needs to previously set group numbers for terminal 200.

Hereinafter, group number setting methods 1 to 4 as in the case ofEmbodiment 2 (FIGS. 15A and 15B and FIG. 16) will be described.

<Setting Method 1>

Setting method 1 is a method whereby a group number is set for eachUL-DL configuration. That is, according to setting method 1, a groupnumber is set for each UL-DL configuration and 1 bit per UL-DLconfiguration is indicated (1 bit/1 Config).

As an example of setting method 1, there is a method as shown in FIG.15A whereby 1 bit (when the maximum number of groups is two) or 2 bits(when the maximum number of groups is three or four) per UL-DLconfiguration is/are indicated (method 1-1). In FIG. 15A, group number‘1’ is indicated for Configs 0 to 2, 5 and 6 and group number ‘2’ isindicated for Configs 3 and 4.

Furthermore, another example of setting method 1 is a method as shown inFIG. 15B whereby a plurality of correspondence tables in which UL-DLconfigurations and group numbers are previously set are provided and anumber indicating which correspondence table is used (number of acorrespondence table) is indicated (method 1-2).

Furthermore, a further example of setting method 1 is a method whereby agroup number is fixedly set for each UL-DL configuration (method 1-3).In this case, signaling from base station 100 to terminal 200 toindicate the group number is unnecessary.

In setting method 1, since a group number is set for each UL-DLconfiguration, the same UL-DL configuration cannot be set amongdifferent groups.

<Setting Method 2>

Setting method 2 is a method whereby a group number is set for eachcomponent carrier set for terminal 200. That is, according to settingmethod 2, a group number is set for each component carrier and 1 bit percomponent carrier is indicated (1 bit/1 CC).

That is, since base station 100 needs to indicate the group number setin each component carrier for each terminal 200, the number of bits forsignaling increases compared to setting method 1. However, there is nosetting limitation shown in setting method 1. That is, according tosetting method 2, the same UL-DL configuration can also be set amongdifferent groups. That is, the same UL-DL configuration may belong togroup 1 or group 2 depending on the terminal.

Setting method 2 can be further subdivided into a method whereby a groupnumber is set for each component carrier set for terminal 200 (method2-1) and a method whereby a component carrier which becomes aninter-group or intra-group cross-carrier scheduling source is configuredfor each terminal 200 (method 2-2). In method 2-2, only a componentcarrier which becomes an inter-group or intra-group cross-carrierscheduling source is indicated to terminal 200. For this reason, it isnecessary to previously set whether to determine between base station100 and terminal 200 which are other component carriers that belong tothe same group as that of the indicated component carrier, fixedly orchangeably by a setting.

<Setting Method 3>

Setting method 3 is a method whereby switching ON/OFF of grouping(whether or not to perform grouping) is indicated for each terminal 200.That is, setting method 3 indicates only 1 bit. Note that setting method3 may be singly set between base station 100 and terminal 200 or settingmethod 3 may be set in combination with setting method 1 or settingmethod 2.

<Setting Method 4>

Setting method 4 is a method whereby only one group is always set foreach terminal 200. In that case, such a limitation is provided that aUL-DL configuration that cannot be included in a component carrier of ahighest-order UL-DL configuration including DL subframe timings shouldnot be set.

Group number setting methods 1 to 4 have been described so far.

In this way, in the present embodiment, base station 100 and terminal200 group a first component carrier and a second component carrier.Here, in a UL-DL configuration set in the first component carrier, a DLsubframe is set at least at the same timing as that of a DL subframe ofa UL-DL configuration set in the second component carrier. Base station100 then indicates resource assignment information for both PDSCHs ofthe first component carrier and the second component carrier to terminal200 using a PDCCH (downlink control channel) assigned to the firstcomponent carrier during cross-carrier scheduling. On the other hand,terminal 200 identifies PDSCH resources received in the first componentcarrier and second component carrier on the basis of the PDCCH receivedin the first component carrier. That is, the first component carrier isassumed to be a cross-carrier scheduling source and the second componentcarrier is assumed to be a cross-carrier scheduling destination.

It is thereby possible to instruct PDSCH assignment at any subframetiming in a specific component carrier (component carrier in which ahighest-order UL-DL configuration including DL subframe timings in thegroup or between groups is set) among a plurality of component carriersset for terminal 200. Moreover, the possibility of a PDCCH becominginsufficient decreases even when the PDCCH indicating a PDSCH of anothercomponent carrier in the specific component carrier (component carrierhaving the highest proportion of DL subframes among component carriersset for terminal 200) during cross-carrier scheduling.

That is, according to the present embodiment, when ARQ is applied tocommunication using an uplink component carrier and a plurality ofdownlink component carriers associated with the uplink componentcarrier, and when the UL-DL configuration set for each component carrier(ratio between UL subframes and DL subframes) varies, it is possible toperform cross-carrier scheduling in any subframe while preventing thePDCCH from becoming insufficient.

In the present embodiment, the component carrier grouping method is notlimited to the example shown in FIG. 19A. For example, in the UL-DLconfiguration shown in FIG. 18B, Config 3, Config 4 and Config 5 may begrouped as group 1 and only Config 2 may be grouped as group 2.

Furthermore, in FIG. 18B, when higher-order Config 5 including ULsubframe timings is set in a component carrier in common to Config 2 andConfig 4 which have no inclusion relation, Config 5, Config 2 and Config4 may be grouped as the same group.

Furthermore, in the UL-DL configuration shown in FIG. 18B, Config 3 andConfig 5 may be grouped as group 1, Config 2 may be grouped as group 2and Config 4 may be grouped as group 3. That is, as the inclusionrelations shown in FIG. 18B, mutually not neighboring UL-DLconfigurations (e.g., Config 3 and Config 5) may be grouped into thesame group.

For example, in FIG. 19A, the UL-DL configurations (Configs. 2, 3, 4, 5)of the component carriers configured for terminal 200 include Config 5which is the highest-order UL-DL configuration among the UL-DLconfigurations shown in FIG. 18. Thus, all the UL-DL configurations(Config 2, 3, 4, 5) may be grouped into one group 1.

That is, terminal 200 may perform grouping so as to prevent groups frombeing formed of only combinations of UL-DL configurations mutuallyhaving no inclusion relation of DL subframe timings (Config 1 and Config3, Config 2 and Config 3, and, Config 2 and Config 4 in FIG. 18B).

Moreover, there can also be a plurality of component carriers in which ahighest-order UL-DL configuration including DL subframe timings is setin the same group. That is, there can also be a plurality of componentcarriers in which the same highest-order UL-DL configuration includingDL subframe timings is set. In this case, when there is a PCell in thegroup, the PCell may be configured as a cross-carrier scheduling source.On the other hand, when there is no PCell in the group (when the groupis formed of only SCells), an SCell of a smaller SCell index may be setas a cross-carrier scheduling source. However, the component carrierwhich becomes a cross-carrier scheduling source between groups(inter-group) need not always be a PCell. Similarly, the componentcarrier which becomes a cross-carrier scheduling source in a group(intra-group) need not always be a PCell. Moreover, when a PCell is nota component carrier which becomes a cross-carrier scheduling sourcebetween groups or in a group, the PCell may be reset as a componentcarrier which becomes a cross-carrier scheduling source.

A common grouping method or individual grouping methods may be adoptedfor the method of grouping component carriers relating to a componentcarrier determining method for reporting results of error detectionusing inclusion relations of UL subframe timings (see FIG. 12), and themethod of grouping component carriers relating to a method ofdetermining a component carrier which becomes a cross-carrier schedulingsource between groups or in a group using inter-group or intra-groupinclusion relations of DL subframe timings described in the presentembodiment (see FIG. 18). When a common grouping method is adopted, thenumber of bits for signaling from base station 100 to terminal 200 canbe reduced using common signaling. Furthermore, adopting the commongrouping method can simplify the operation during processing when addingnew component carriers as shown in FIG. 14 and can thereby simplify theconfigurations of base station 100 and terminal 200.

For example, it is assumed that grouping relating to indication ofresults of error detection (grouping using inclusion relations of ULsubframe timings) is used for grouping relating to cross-carrierscheduling for reporting results of error detection and forcross-carrier scheduling, when a common grouping method is adopted. Inthis case, depending on UL-DL configurations of component carriers to begrouped, there is a possibility that a plurality of UL-DL configurationshaving no inclusion relation may become the highest-order UL-DLconfigurations in the group in cross-carrier scheduling. For example,when Configs. 1, 2 and 4 are grouped into one group, Config 1 becomesthe highest-order UL-DL configuration in the inclusion relations of ULsubframe timings (FIG. 12A), whereas Configs 2 and 4 mutually having noinclusion relation become the highest-order UL-DL configurations in theinclusion relations of DL subframe timings (FIG. 18A).

In this case, a component carrier of a UL-DL configuration having moreDL subframes (Config 4 in the above example) among a plurality of UL-DLconfigurations having no inclusion relation may be configured as acomponent carrier which becomes a cross-carrier scheduling source in thepresent embodiment. Alternatively, a common grouping method may also beadopted so as not to accept grouping whereby a plurality of UL-DLconfigurations mutually having no inclusion relation become thehighest-order UL-DL configurations for reporting results of errordetection and for cross-carrier scheduling.

Embodiment 4

FIGS. 23A and 23B illustrate UL-DL configurations of a terminalaccording to Embodiment 4 of the present invention.

For a terminal in which a certain component carrier (suppose Cell A) isconfigured as a PCell, a UL-DL configuration set for the PCell isindicated by a broadcast signal (SIB1). For another terminal in whichthe component carrier (Cell A) is configured as an SCell, a UL-DLconfiguration set for the SCell is indicated by radio resource control(RRC) which is terminal-specific signaling.

As shown in FIG. 23A, a plurality of component carriers (Cell A₁ andCell A₂) in the same frequency band (Band A (e.g., 2-GHz band)) are usedin intra-band CA. A case will be described where a base stationconfigures a certain terminal with Cell A₁ as a PCell and Cell A₂ as anSCell. A UL-DL configuration set in the PCell is indicated by abroadcast signal (SIB1) common (cell specific) to a plurality ofterminals in Cell A₁. A UL-DL configuration set in the SCell isindicated by RRC which is terminal-specific signaling in Cell A₁.However, in intra-band CA, a UL-DL configuration of the SCell (Cell A₂)indicated by RRC is set to the same value as that of a UL-DLconfiguration indicated by a broadcast signal (SIB1) common to aplurality of terminals in Cell A₂. Furthermore, in a plurality ofcomponent carriers in the same frequency band, the same UL-DLconfiguration is used to avoid interference between uplink communicationand downlink communication. Thus, the terminal operates in expectationthat in inter-band CA, the UL-DL configuration in the SCell will be thesame UL-DL configuration as that indicated to the terminal using thebroadcast signal (SIB1) in the PCell.

As shown in FIG. 23B, in inter-band CA, component carriers (Cell A andCell B) in different frequency bands (Band A (e.g., 2-GHz band) and BandB (e.g., 800-MHz band)) are used. A case will be described as an examplewhere the base station configures Cell A as the PCell and Cell B as theSCell for a certain terminal. A UL-DL configuration set in the PCell ofthe terminal is indicated by a broadcast signal (SIB1) common to aplurality of terminals in Cell A. A UL-DL configuration set in the SCellis indicated by RRC which is terminal-specific signaling in Cell A.However, in inter-band CA, studies are underway to set the UL-DLconfiguration of the SCell (Cell B) indicated by RRC to a valuedifferent from that of the UL-DL configuration indicated by a broadcastsignal (SIB1) common to a plurality of terminals in Cell B. That is, asUL-DL configurations set in one component carrier, studies are underwayto manage one UL-DL configuration indicated by a broadcast signal and aUL-DL configuration indicated by terminal-specific RRC signalingidentical to the UL-DL configuration indicated by a broadcast signalthereof, and in addition, a UL-DL configuration indicated byterminal-specific RRC which is different from the UL-DL configurationindicated by the broadcast signal. Furthermore, studies are underway tocause the base station to indicate one UL-DL configuration to a terminalas a UL-DL configuration corresponding to the component carrier using abroadcast signal or RRC on one hand, and cause the base station tochange a UL-DL configuration indicated to a terminal from one terminalto another on the other.

In the LTE-A system, studies are also underway to temporally switch aUL-DL configuration indicated by SIB1 in accordance with a variation inthe ratio between uplink communication traffic and downlinkcommunication traffic through RRC signaling or dynamic indication.

In relation with Embodiment 2, the present embodiment focuses attentionon inclusion relations of UL subframe timings between UL-DLconfigurations set in each component carrier configured for terminal200. As UL-DL configurations set in one component carrier, the presentembodiment focuses attention on management of one UL-DL configurationindicated by a broadcast signal and a UL-DL configuration indicated byterminal-specific RRC signaling identical to the UL-DL configurationindicated by a broadcast signal thereof, and in addition, a UL-DLconfiguration indicated by terminal-specific RRC signaling which isdifferent from the UL-DL configuration indicated by the broadcastsignal. Moreover, the present embodiment also focuses attention onindication, as UL-DL configurations set in one component carrier, oneUL-DL configuration to a terminal using a broadcast signal or RRCsignaling, while causing the UL-DL configuration to be indicated to theterminal to vary from one terminal to another.

Although the present embodiment does not limit the number of groups,only a case will be described where the number of groups is one forsimplicity of description. That is, response signals indicating resultsof error detection reported by a terminal to a base station are alwaysreported using only one component carrier (PCell).

FIG. 24 illustrates settings of UL-DL configurations that satisfycondition (1) in Embodiment 4 of the present invention.

Since a terminal always reports a response signal indicating results oferror detection using only one component carrier, UL-DL configurationsof an SCell used by the terminal corresponding to UL-DL configurationsof a PCell indicated by a broadcast signal (SIB1) are as condition (1)shown in FIG. 24. This is none other than the inclusion relations of ULsubframe timings in FIG. 12A and FIG. 12B according to Embodiment 2expressed in the form of a table. For example, it can be read from FIG.12A and FIG. 12B that UL subframe timings of Config #1 include Config#1, Config #2, Config #4 or Config #5. On the other hand, in FIG. 24,when the UL-DL configuration indicated in the PCell by the base stationusing a broadcast signal (SIB1) is Config #1, the UL-DL configuration ofthe SCell used by the terminal is Config #1, Config #2, Config #4 orConfig #5, and the terminal always reports a response signal indicatingresults of error detection using only the PCell. Here, the “UL-DLconfiguration of the SCell used by the terminal” may be indicated to theterminal in the PCell by terminal-specific RRC or may be dynamicallyindicated to the terminal individually. The “UL-DL configuration of theSCell used by the terminal” may be different from the UL-DLconfiguration indicated by the base station to the other terminal usinga broadcast signal (SIB1) in the component carrier used by the terminalas the SCell. The same will apply to the description, hereinafter.

A UL-DL configuration is information indicating a relationship as towhich subframe corresponds to a UL subframe or DL subframe in one frame(10 subframes) shown in FIG. 3. When a UL-DL configuration isindividually indicated to a terminal dynamically, that is, for eachsubframe, the UL-DL configuration need not always be informationindicating a relationship as to which subframe corresponds to a ULsubframe or DL subframe in one frame. For example, in this case, theUL-DL configuration may be information indicating a relationship as towhich subframe is a UL subframe or DL subframe among a plurality ofsubframes. Alternatively, the UL-DL configuration may be informationindicating which of a UL subframe or DL subframe one subframecorresponds to. The same will apply to the description, hereinafter.

A case will be described with reference to FISG. 25A and 25B where aUL-DL configuration of an SCell used by a terminal is different from aUL-DL configuration indicated by the base station in the same componentcarrier using a broadcast signal (SIB1). Particularly, a case will bedescribed in detail where Cell B used as an SCell by a terminal carryingout inter-band CA is used as a PCell by a terminal not carrying out CA.

FIGS. 25A and 25B illustrate problems with CRS measurement in thepresent embodiment. In FIG. 25A, when UL subframe timings of a UL-DLconfiguration of Cell B indicated by the base station using a broadcastsignal (SIB1) include (or may be equal to) UL subframe timings of aUL-DL configuration of an SCell (Cell B) used by the terminal (assumedto be condition (2)), Config #2 is set, for example, in an SCell of aninter-band CA terminal and Config #1 is set in a PCell of a non-CAterminal using Cell B which is the same component carrier. In the samesubframe within the same component carrier, a plurality of terminals mayrecognize different communication directions of subframes. That is,there are subframes in which UL and DL conflict with each other. Thebase station performs scheduling so that only one of uplinkcommunication and downlink communication occurs. In FIG. 25B, when ULsubframe timings of a UL-DL configuration of an SCell (Cell B) used by aterminal include (and are also different from) UL subframe timings of aUL-DL configuration of Cell B indicated by the base station using abroadcast signal (SIB1), for example, Config #1 is set in an SCell of aninter-band CA terminal and Config #2 is set in a PCell of a non-CAterminal using Cell B which is the same component carrier. In this case,a communication direction of a subframe recognized by the terminal inthe same subframe within the same component carrier may be different,but as in the case of FIG. 25A, the base station performs scheduling sothat only one of uplink communication and downlink communication occurs.

However, in FIG. 25B, the non-CA terminal (especially a legacy terminalthat cannot provide a limitation to subframes for measuring a CRS(Cell-specific Reference Signal) (e.g., terminal of Rel-8 or Rel-9))measures CRS in DL subframes for mobility measurement. That is, insubframes in which UL and DL conflict with each other, even when thebase station attempts to prevent downlink communication from occurringto use the subframes as UL subframes, there may be a terminal thatperforms reception processing in a DL subframe. In this case, inter-bandCA terminals carrying out uplink communication provide interference tonon-CA terminals that perform CRS measurement. On the other hand, inFIG. 25A, when the non-CA terminal is in a UL subframe, the inter-bandCA terminal is in a DL subframe, and CRS measurement may occur. However,since terminals that support inter-band CA are terminals of Rel-11 orlater, if the base station provides a limitation to CRS measurement forterminals of Rel-10 or later, this interference can be avoided.Therefore, condition (2) shown in FIG. 25A is necessary to avoidinterference to CRS measurement in terminals of Rel-8 or Rel-9.

FIG. 26 illustrates settings of UL-DL configurations that satisfycondition (1) and condition (2) according to Embodiment 4 of the presentinvention.

In the present embodiment, as shown in FIG. 26, UL-DL configurations ofthe SCell used by the terminal satisfy condition (1) and condition (2),simultaneously. That is, the base station determines a UL-DLconfiguration of the SCell used by the terminal on the basis of a UL-DLconfiguration indicated by the base station using a broadcast signal(SIB1) in a component carrier used by the terminal as the PCell and aUL-DL configuration indicated by the base station using a broadcastsignal (SIB1) in a component carrier used by the terminal as the SCell.When different UL-DL configurations are used among a plurality ofterminals using the same component carrier, it is possible to avoidinterference to mobility measurement (CRS measurement) in legacyterminals while simplifying an RF configuration of the terminals byreporting response signals indicating results of error detection usingonly one component carrier (PCell).

Under condition (2), it is possible to prevent a non-CA terminal fromperforming CRS measurement, by setting the subframe, for example, as anMBSFN subframe. Alternatively, interference will no longer occur if alegacy terminal without limitations on CRS measurement is prevented fromusing the frequency band. Therefore, at least condition (1) may besatisfied.

FIG. 27 illustrates problems with SRS transmission according to thepresent embodiment.

In FIG. 27, UL subframe timings of a UL-DL configuration of Cell Bindicated by the base station using a broadcast signal (SIB1) include(or may be equal to) UL subframe timings of a UL-DL configuration of anSCell (Cell B) used by the terminal (assumed to be condition (2)).

Condition (2) will be described in detail with reference to FIG. 27. Asdescribed above, condition (2) makes it possible to prevent aninter-band CA terminal carrying out uplink communication from providinginterference to a legacy terminal carrying out CRS measurement. However,according to condition (2), when a subframe in the SCell of aninter-band CA terminal is a DL subframe, a subframe of a non-CA terminalin the same component carrier may be a UL subframe. In this subframe,when the non-CA terminal transmits an SRS (sounding reference signal)(that is, periodic SRS) previously set from the base station so as to betransmitted periodically, UL transmission by the non-CA terminal mayprovide interference to DL reception in the SCell of the inter-band CAterminal using the same component carrier.

Thus, the base station indicates the subframe in which an SRS istransmitted from another terminal to the inter-band CA terminal using,for example, RRC. The inter-band CA terminal then determines whether ornot an SRS has been transmitted from the other terminal in thecorresponding subframe on the basis of the information. Since an SRS isalways transmitted using only the last two symbols among 14 symbols ofone subframe, the terminal receives a maximum of 12 symbols except thelast two symbols in the subframe. However, in the subframe, the basestation needs to perform both downlink transmission and uplink SRSreception, and fewer than 12 symbols can actually be used for downlinkcommunication when a transmission/reception switching time in the basestation or a propagation delay between the base station and the terminalis taken into consideration. The operation is similar to an operation ina special subframe. Therefore, the inter-band CA terminal may regard thesubframe as a special subframe.

The form of information as to which subframe is used to transmit an SRSfrom another terminal may be a bitmap pattern indicating an SRStransmission subframe or SRS non-transmission subframe. The base stationand the terminal may store a table of index numbers associated withpatterns of SRS transmission subframes in a one-to-one correspondence,and the form of the information as to which subframe is used to transmitthe SRS from the other terminal may be an index number thereof. The formof the information may also be a UL-DL configuration for identifying anSRS transmission subframe. In this case, the inter-band CA terminaldetermines that an SRS is transmitted from the other terminal in a ULsubframe indicated by the UL-DL configuration for identifying the SRStransmission subframe. When the UL-DL configuration set for theinter-band CA terminal indicates a DL subframe in the UL subframeindicated by the UL-DL configuration for identifying an SRS transmissionsubframe, the inter-band CA terminal regards the subframe as a specialsubframe. In the example in FIG. 27, the base station indicates Config#1 to the inter-band CA terminal using, for example, using RRC as theUL-DL configuration for identifying an SRS transmission subframe. Theinter-band CA terminal regards subframe #3 and subframe #8 which becomeDL subframes in Config #2 used in the inter-band CA terminal and ULsubframes in Config #1 as special subframes. In a most preferredembodiment, condition (2) and signaling indicating which subframe isused to transmit an SRS from the other terminal should be appliedsimultaneously, but any one of these may be applicable.

Interference is provided to mobility measurement (CRS measurement) inthe non-CA terminal only when UL transmission is performed in the SCellof the inter-band CA terminal as shown in FIG. 25B. In other words, theabove-described interference problem does not occur in a terminal thatcannot perform UL transmission from the SCell during inter-band CA forRF configuration-related reasons, for example. Thus, the method ofsetting the UL-DL configuration of the SCell used by the terminal may bechanged on the basis of UE capability (terminal capability) indicatedfrom the terminal to the base station. That is, the base station may setthe UL-DL configuration of the SCell used by a terminal that satisfiesonly condition (1) shown in FIG. 24 for a terminal that cannot performUL transmission from the SCell and set the UL-DL configuration of theSCell used by a terminal that satisfies condition (1) and condition (2)shown in FIG. 26 for a terminal that can perform UL transmission fromthe SCell. In this case, the base station determines the UL-DLconfiguration of the SCell used by a terminal that cannot perform ULtransmission from the SCell on the basis of only the UL-DL configurationindicated by the base station using a broadcast signal (SIB1) of thecomponent carrier.

As one of UE capabilities, full duplex and half duplex can be consideredin addition to the capability of UL transmission in the SCell. Whencarrier aggregation (that is, inter-band carrier aggregation) isperformed between a component carrier (Cell A) of a certain frequencyband (Band A) and a component carrier (Cell B) of a frequency band (BandB) different therefrom, a terminal that can perform UL transmissionusing the component carrier of one frequency band and perform DLreception using the component carrier of the other frequency band is afull duplex terminal, and a terminal that cannot perform the abovetransmission and reception simultaneously is a half duplex terminal. Thehalf duplex terminal that can simplify RF is preferred for a low-costterminal and the full duplex terminal is preferred for a high-endterminal. The above-described UE capability of being unable to performUL transmission in the SCell is intended for a low-cost terminal and theUE capability of being able to perform UL transmission in the SCell isintended for a high-end terminal. Thus, the base station may set a UL-DLconfiguration of the SCell used by a terminal that satisfies condition(1) shown in FIG. 24 for a low-cost half duplex terminal and may set aUL-DL configuration of the SCell used by a terminal that satisfiescondition (1) and condition (2) shown in FIG. 26 for a high-end fullduplex terminal.

Furthermore, when a half duplex terminal performs inter-band CA, ifUL-DL configurations set for the terminal differ between componentcarriers, there are subframes in which UL and DL conflict with eachother between the component carriers. In this case, the half duplexterminal can use only UL subframes or DL subframes of the one componentcarrier in the above-described subframes, so that there is a problem inthat the improvement of a peak rate which is the original object ofcarrier aggregation is not achieved.

FIG. 28 illustrates UL-DL configuration settings that satisfy condition(3) according to Embodiment 4 of the present invention.

As shown in FIG. 28, in order to solve the above-described problem, thebase station may set the UL-DL configuration of the SCell used by thehalf duplex terminal to the same value (that is, condition (3) describedin FIG. 28) as that of the UL-DL configuration indicated by a broadcastsignal (SIB1) of the component carrier used by the half duplex terminalas the PCell. This allows the communication direction of the PCell toalways match that of the SCell, and thus eliminates subframes in whichcommunication is impossible, and can thereby achieve the improvement ofa peak rate which is the original object of carrier aggregation. Thatis, the base station may set, for the full duplex terminal, a UL-DLconfiguration of the SCell used by the terminal that satisfies condition(1) and condition (2) shown in FIG. 26 and set, for the half duplexterminal, a UL-DL configuration of the SCell used by the terminal thatsatisfies condition (3). Alternatively, the base station may also set,for a full duplex terminal capable of UL transmission in the SCell, aUL-DL configuration of the SCell used by the terminal that satisfiescondition (1) and condition (2) shown in FIG. 26, set, for a full duplexterminal not capable of UL transmission in the SCell, a UL-DLconfiguration of the SCell used by the terminal that satisfies condition(1) shown in FIG. 24, and set, for a half duplex terminal, a UL-DLconfiguration of the SCell used by the terminal that satisfies condition(3) shown in FIG. 28. Moreover, the base station may indicate to theterminal, signaling indicating which subframe is used to transmit an SRSfrom another terminal. It is clear from FIG. 28 and FIG. 24 thatcondition (3) is included in condition (1).

Here, under condition (3), the UL-DL configuration of the PCell is setso as to be equal to the UL-DL configuration of the SCell and thereseems to be no major difference from the case with intra-band CA asshown in FIG. 23A. What condition (3) means is that when the UL-DLconfiguration indicated by the base station using a broadcast signal(SIB1) in a component carrier used by the terminal as a PCell isdifferent from the UL-DL configuration indicated by the base stationusing a broadcast signal (SIB1) in a component carrier used by theterminal as an SCell, the UL-DL configuration of the SCell used by theterminal is the same as the UL-DL configuration indicated by the basestation using a broadcast signal (SIB1) in the component carrier used bythe terminal as the PCell. On the other hand, FIG. 23A means that theUL-DL configuration of the SCell used by the terminal is the same as theUL-DL configuration indicated by the base station using a broadcastsignal (SIB1) in the component carrier used by the terminal as theSCell. Condition (3) is different from FIG. 23A in the above respect.

Of condition (1), condition (2) and condition (3) of the presentembodiment, condition (1) and condition (3) are limitations on the UL-DLconfiguration of the PCell and the UL-DL configuration of the SCell setfor one terminal. Condition (2) is a limitation on the UL-DLconfiguration set among a plurality of terminals. The terminal cannotknow what kind of UL-DL configuration is set by the base station forother terminals using the same component carrier. For this reason, theterminal cannot determine whether or not to apply condition (2). On theother hand, since the base station naturally knows what kind of UL-DLconfiguration is set for each terminal, the base station can determinewhether or not to apply condition (2). Furthermore, the base station andthe terminal can naturally know information on which subframe is used totransmit an SRS from the other terminal because such information isindicated from the base station to the terminal.

As described above, in the present embodiment, there are four conditionscorresponding to UL-DL configurations and signaling methods for theterminal as shown below. The following conditions and signaling methodsmay differ from one terminal to another. For example, the followingconditions and signaling methods may be made to vary from one terminalto another on the basis of UE capability.

1. Only condition (1) is applied.

2. Only condition (3) is applied.

3. In addition to the application of only condition (1), information onwhich subframe is used to transmit an SRS from the other terminal isindicated.

4. In addition to the application of only condition (3), information onwhich subframe is used to transmit an SRS from the other terminal isindicated.

Furthermore, in the present embodiment, there are eight conditionscorresponding to UL-DL configurations and signaling methods for the basestation as shown below. The following conditions and signaling methodsmay be made to differ from one terminal to another (e.g., on the basisof UE capability) or from one frequency band to another.

1. Only condition (1) is applied.

2. Only condition (3) is applied.

3. In addition to the application of only condition (1), information onwhich subframe is used to transmit an SRS from the other terminal isindicated.

4. In addition to the application of only condition (3), information onwhich subframe is used to transmit an SRS from the other terminal isindicated.

5. Condition (1) and condition (2) are applied.

6. Condition (3) and condition (2) are applied.

7. In addition to the application of condition (1) and condition (2),information on which subframe is used to transmit an SRS from the otherterminal is indicated.

8. In addition to the application of condition (3) and condition (2),information on which subframe is used to transmit an SRS from the otherterminal is indicated.

Thus, the present embodiment has focused attention on inclusionrelations of UL subframe timings among UL-DL configurations ofrespective component carriers configured for terminal 200. Furthermore,as UL-DL configurations set in one component carrier, the presentembodiment has focused attention on management of one UL-DLconfiguration indicated by a broadcast signal and a UL-DL configurationindicated by terminal-specific RRC signaling identical to the UL-DLconfiguration indicated by the broadcast signal, and in addition, aUL-DL configuration indicated by terminal-specific RRC signaling whichis different from the UL-DL configuration indicated by the broadcastsignal. Moreover, the present embodiment has also focused attention onindicating one UL-DL configuration to a terminal using a broadcastsignal or RRC signaling as a UL-DL configuration for the componentcarrier, meanwhile causing the UL-DL configuration to be indicated tothe terminal to vary from one terminal to another. By adding condition(1), condition (2) and condition (3) to the setting of a UL-DLconfiguration, it is possible to avoid interference to CRS measurementprovided for a Rel-8 or Rel-9 terminal while reporting response signalsindicating results of error detection to be reported from the terminalto the base station always using only one component carrier (PCell). Atthe same time, it is possible to avoid interference by periodic SRStransmission by indicating information on which subframe is used totransmit an SRS from the other terminal to the terminal.

Furthermore, condition (1), condition (2) and condition (3) of thepresent embodiment are based on a premise that the UL-DL configurationof the PCell used by the terminal is the same as the UL-DL configurationindicated by the base station using a broadcast signal (SIB1) in acomponent carrier used by the terminal as a PCell. Therefore, the basestation determines the UL-DL configuration of the SCell used by theterminal on the basis of the UL-DL configuration indicated by the basestation using a broadcast signal (SIB1) at least in a component carrierused by the terminal as a PCell. However, what is important is that theUL-DL configuration set in the component carrier used by the terminal asthe PCell is not the UL-DL configuration indicated by the base stationusing a broadcast signal (SIB1) but the UL-DL configuration of the PCellused by the terminal. In short, a similar problem can be solved evenwhen the UL-DL configuration of the SCell used by the terminal isdetermined based on at least the UL-DL configuration of the PCell usedby the terminal. Therefore, the present embodiment can be implementedeven when the UL-DL configuration of the PCell used by the terminal isdifferent from the UL-DL configuration indicated by the base stationusing a broadcast signal (SIB1) in the component carrier used by theterminal as the PCell, for example, when the UL-DL configuration of thePCell used by the terminal is indicated not by SIB1 but RRC ordynamically.

A case has been described in the present embodiment where a UL-DLconfiguration set for an inter-band CA terminal differs from onecomponent carrier to another. However, the present embodiment is notnecessarily limited to inter-band CA. Especially, condition (2) needsonly to satisfy a requirement of managing, as UL-DL configurations setin one component carrier, one UL-DL configuration indicated by abroadcast signal and a UL-DL configuration indicated byterminal-specific RRC signaling identical to the UL-DL configurationindicated by a broadcast signal thereof, and in addition, a UL-DLconfiguration indicated by terminal-specific RRC signaling which isdifferent from the UL-DL configuration indicated by the broadcastsignal, and a requirement of indication, as UL-DL configurations set inone component carrier, one UL-DL configuration to a terminal, using abroadcast signal or RRC signaling, while causing the UL-DL configurationto be indicated to the terminal to vary from one terminal to another.The above-described case will be shown in Embodiment 5.

Embodiment 5

The present embodiment will focus attention on the case in Embodiment 4where only condition (2) is applied. The present embodiment needs onlyto satisfy a requirement of managing, as UL-DL configurations set in onecomponent carrier, one UL-DL configuration indicated by a broadcastsignal and a UL-DL configuration indicated by terminal-specific RRCsignaling identical to the UL-DL configuration indicated by a broadcastsignal thereof, and in addition, a UL-DL configuration indicated byterminal-specific RRC signaling which is different from the UL-DLconfiguration indicated by the broadcast signal, and a requirement ofindication, as UL-DL configurations set in the component carrier, oneUL-DL configuration to a terminal using a broadcast signal or RRCsignaling, meanwhile causing the UL-DL configuration to be indicated tothe terminal to vary from one terminal to another. Therefore, thepresent embodiment is not dependent on the presence or absence ofinter-band CA.

A case will be described with reference to FIGS. 29A and 29B where twoUL-DL configurations: a UL-DL configuration indicated by a base stationusing SIB1 in one component carrier (PCell) and a UL-DL configurationindicated by RRC signaling or indicated dynamically, are set one by onefor different terminals.

FIGS. 29A and 29B illustrate problems with CRS measurement in thepresent embodiment.

In FIGS. 29A and 29B, UL subframe timings of a UL-DL configurationindicated by the base station using a broadcast signal (SIB1) include(may also be equal to) UL subframe timings of a UL-DL configurationindicated by the terminal by RRC signaling or indicated dynamically(assumed to be condition (2)).

However, terminals that can set a UL-DL configuration indicated by thebase station by RRC signaling or indicated dynamically are terminals ofRel-11 or later and are terminals that can provide a limitation on CRSmeasurement. On the other hand, terminals that can set a UL-DLconfiguration indicated by the base station using SIB1 are all terminalsof Rel-8 or later, and of those terminals, terminals that can provide alimitation on CRS measurement are terminals of Rel-10 or later.

FIG. 29A illustrates a case where UL subframe timings of a UL-DLconfiguration indicated by the base station using a broadcast signal(SIB1) include (may also be equal to) UL subframe timings of a UL-DLconfiguration indicated by the terminal by RRC signaling or indicateddynamically (assumed to be condition (2)). For example, Config #2 is setfor Rel-11 terminal A and Config #1 is set for terminal B of Rel-8, 9,10 or 11 of the same component carrier. In this case, in the samesubframe within the same component carrier, the communication directionof a subframe recognized by terminal A and terminal B may differ. Thatis, there are subframes in which UL and DL conflict with each other. Inthis case, the base station performs scheduling in such a way that onlyone of uplink communication and downlink communication occurs.Furthermore, the base station provides a limitation on CRS measurementof terminal A so as to prevent Rel-11 terminal A from performing CRSmeasurement during UL transmission of terminal B. Next, FIG. 29Billustrates a case where UL subframe timings of a UL-DL configurationindicated by the base station by RRC signaling or indicated dynamicallyinclude (and are different from) UL subframe timings of a UL-DLconfiguration indicated by the base station using a broadcast signal(SIB1). For example, Config #1 is set for Rel-11 terminal A and Config#2 is set for terminal B of Rel-8, 9, 10 or 11 using the same componentcarrier. In this case, in the same subframe within the same componentcarrier, the communication direction of a subframe recognized byterminal A and terminal B may differ. That is, there are subframes inwhich UL and DL conflict with each other. In this case, the base stationperforms scheduling in such a way that only one of uplink communicationand downlink communication occurs.

In FIG. 29B, terminal B of Rel-8 or Rel-9 not subject to a limitation onCRS measurement performs CRS measurement in DL subframes for mobilitymeasurement. That is, in subframes in which UL and DL conflict with eachother, even when the base station prevents downlink communication fromoccurring so that those subframes may be used as UL subframe, there areterminals that perform reception processing in DL subframes. Therefore,at this time, terminal A that performs uplink communication providesinterference to terminal B that performs CRS measurement, particularly,a terminal of Rel-8 or Rel-9. Thus, condition (2) shown in FIG. 29A isnecessary to avoid interference to CRS measurement in the terminals ofRel-8 or Rel-9. That is, the UL-DL configuration settable by the basestation and indicated by RRC signaling or indicated dynamically isdetermined on the basis of a UL-DL configuration indicated by the basestation using a broadcast signal (SIB1).

FIG. 30 illustrates settings of UL-DL configurations that satisfycondition (2) according to Embodiment 5 of the present invention.

UL-DL configurations that can be set by the base station, indicated byRRC signaling or indicated dynamically satisfy FIG. 30.

Furthermore, condition (2) will be described in detail with reference toFIG. 31. FIG. 31 illustrates problems with SRS transmission according tothe present embodiment.

As described above, due to condition (2), Rel-11 terminal A thatperforms uplink communication can prevent interference to Rel-8 or Rel-9terminal B that performs CRS measurement. However, according tocondition (2), when a subframe of Rel-11 terminal A is a DL subframe, asubframe of terminal B using the same component carrier may be a ULsubframe. When terminal B transmits an SRS previously set from the basestation so as to be transmitted periodically in this UL subframe, ULtransmission by terminal B may interfere with DL reception in terminal Ausing the same component carrier.

Therefore, the base station indicates, for example, by RRC signaling, asto which subframe is used to transmit an SRS from another terminal to aterminal (that is, terminal A) using a UL-DL configuration indicated byRRC signaling or indicated dynamically. The terminal then determineswhether or not the SRS has been transmitted from the other terminal inthe corresponding subframe on the basis of the information. Since an SRSis always transmitted only in last two symbols of 14 symbols of onesubframe, the terminal receives a maximum of 12 symbols except the lasttwo symbols in the subframe. However, in the subframe, the base stationneeds to perform both downlink transmission and uplink SRS reception,and fewer than 12 symbols can actually be used for downlinkcommunication when a time of switching between transmission andreception in the base station or a propagation delay between the basestation and the terminal is taken onto consideration. Moreover, theoperation is similar to an operation in a special subframe. Therefore,the terminal using a UL-DL configuration indicated by RRC signaling orindicated dynamically may regard the subframe as a special subframe. Inthe most preferred embodiment, condition (2) and signaling indicatingwhich subframe is used to transmit an SRS from another terminal shouldbe applied simultaneously, but any one of these may be applied.

The form of information on which subframe is used to transmit an SRSfrom the other terminal may be a bitmap pattern indicating an SRStransmission subframe or SRS non-transmission subframe. A table of indexnumbers associated with patterns of SRS transmission subframes in aone-to-one correspondence may be stored in the base station andterminal, respectively, and the form of information on which subframe isused to transmit an SRS from the other terminal may be an index numberthereof. The form of information may also be a UL-DL configuration foridentifying an SRS transmission subframe. In this case, the terminalusing a UL-DL configuration indicated by RRC signaling or indicateddynamically determines that an SRS is transmitted from the otherterminal in a UL subframe indicated by the UL-DL configuration foridentifying an SRS transmission subframe. In the UL subframe indicatedby the UL-DL configuration for identifying an SRS transmission subframe,when the UL-DL configuration set for the terminal indicates a DLsubframe, the terminal regards the subframe as a special subframe. Inthe example of FIG. 31, the base station indicates Config #1 to terminalA as a UL-DL configuration for identifying an SRS transmission subframe,for example, by RRC signaling. A subframe in terminal A becomes a DLsubframe according to Config #2 used by terminal A and becomes a ULsubframe according to Config #1 for identifying an SRS transmissionsubframe and regards subframe #3 and subframe #8 as special subframes.

As described in Embodiment 4, the terminal cannot determine whether ornot condition (2) is applicable. On the other hand, the base station candetermine whether or not condition (2) is applicable. Furthermore, sincethe base station indicates the information on which subframe is used totransmit an SRS from the other terminal to the terminal, the basestation and the terminal can naturally know the information.

As described above, in the present embodiment, there are two conditionscorresponding to UL-DL configurations and SRS-related signaling methodsfor the terminal as shown below. The following conditions and signalingmethods may vary from one terminal to another. For example, thefollowing conditions and signaling methods may vary from one terminal toanother on the basis of UE capability.

1. No condition.

2. Information on which subframe is used to transmit an SRS from anotherterminal is indicated. Furthermore, in the present embodiment, there arethree conditions corresponding to UL-DL configurations and SRS-relatedsignaling methods for the base station as shown below. The followingconditions and signaling methods may vary from one terminal to another(e.g., on the basis of UE capability) or from one frequency band toanother. Terminals that satisfy the conditions and signaling methodsshown in Embodiment 4 may be located within the same component carrier.

1. Information on which subframe is used to transmit an SRS from anotherterminal is indicated.

2. Only condition (2) is applied.

3. In addition to the application of only condition (2), information onwhich subframe is used to transmit an SRS from another terminal isindicated is indicated.

As described above, the present embodiment manages, as UL-DLconfigurations set in one component carrier, one UL-DL configurationindicated by a broadcast signal and a UL-DL configuration indicated byterminal-specific RRC signaling identical to the UL-DL configurationindicated by the broadcast signal, and in addition, a UL-DLconfiguration indicated by terminal-specific RRC signaling which isdifferent from the UL-DL configuration indicated by the broadcastsignal. Furthermore, as UL-DL configurations set in the componentcarrier, when indicating one UL-DL configuration to a terminal using abroadcast signal or RRC signaling, while satisfying a requirement ofcausing the UL-DL configuration to be indicated to the terminal to varyfrom one terminal to another, condition (2) is provided between theUL-DL configuration indicated by the base station using a broadcastsignal (SIB1) and the UL-DL configuration indicated by the base stationby RRC signaling or indicated dynamically. This allows the terminalusing the UL-DL configuration indicated by the base station by RRCsignaling or indicated dynamically to avoid interference with CRSmeasurement provided to terminals of Rel-8 or Rel-9 using the UL-DLconfiguration indicated by the base station using a broadcast signal(SIB1).

Furthermore, in the present embodiment, the base station indicatesinformation on which subframe is used to transmit an SRS from anotherterminal to a terminal using a UL-DL configuration indicated by RRCsignaling or indicated dynamically. This allows the terminal using aUL-DL configuration indicated by the base station using SIB1 to avoidinterference by periodic SRS transmission provided to the terminal usinga UL-DL configuration indicated by the base station by RRC signaling orindicated dynamically.

The embodiments of the present invention have been described so far.

A case has been described in the above embodiments where a common framestarting position is applied among component carriers in which differentUL-DL configurations are set. However, the present invention is notlimited to this, but the present invention is also applicable to a casewhere subframe timings are shifted among component carriers (when asubframe offset exists). For example, as shown in FIG. 20, a subframeoffset may be set between different groups. That is, as shown in FIG.20, the frame starting position is kept the same within each group.

Furthermore, a case has been described in the above embodiments whereConfigs 0 to 6 shown in FIG. 3 are used as UL-DL configurations.However, the UL-DL configurations are not limited to Configs 0 to 6shown in FIG. 3. For example, as shown in FIG. 21, a UL-DL configuration(assumed to be Config 7 here) in which all subframes become DL subframesmay also be used in addition to Configs 0 to 6 shown in FIG. 3. As shownin FIG. 21A, in inclusion relations of UL subframe timings among UL-DLconfigurations, Config 7 in which all subframes become DL subframes is alowest-order UL-DL configuration. In other words, in the inclusionrelations of DL subframe timings among UL-DL configurations, Config 7 inwhich all subframes become DL subframes is a highest-order UL-DLconfiguration (not shown). Furthermore, as shown in FIG. 21B, a timingof reporting results of error detection of a component carrier set withthe UL-DL configuration (Config 7) in which all subframes are DLsubframes is a timing at the fourth subframe after a DL subframe inwhich a PDSCH is received or after the fourth subframe and is anearliest UL subframe timing in a component carrier in which ahighest-order UL-DL configuration (Config 1) including UL subframetimings is set.

In the present embodiment, as shown in FIG. 22, subframes other than ULsubframes, DL subframes and special subframes may also be used. In FIG.22, for example, empty subframes (or blank subframes) in which notransmission/reception is performed to reduce interference to other basestations and terminals (or almost blank subframes (ABS) when channelsfor transmission/reception are limited to some channels) or occupiedsubframes occupied by other radio communication systems or the like areused. Thus, for component carriers in which subframes other than ULsubframes, DL subframes and special subframes exist, even when ahighest-order UL-DL configuration of the component carrier includes ULsubframe timings, the component carrier need not always report resultsof error detection. Likewise, the component carrier need not beconfigured as a cross-carrier scheduling source. When results of errordetection are not reported using the component carrier, the results oferror detection may be reported using a component carrier in which asecond highest-order UL-DL configuration including UL subframe timingsis set. Similarly, when the component carrier is not configured as across-carrier scheduling source, the component carrier in which a secondhighest-order UL-DL configuration including DL subframe timings is setmay be configured as a cross-carrier scheduling source. Furthermore, thetiming of reporting the results of error detection in component carriersin which there are subframes other than UL subframes, DL subframes andspecial subframes may be a timing at the fourth subframe after a DLsubframe in which a PDSCH is received or after the fourth subframe, andan earliest UL subframe timing in a component carrier in which ahighest-order UL-DL configuration including UL subframe timings is set.Alternatively, results of error detection in the component carrier inwhich subframes other than UL subframes, DL subframes and specialsubframes exist may be reported at the same timing as the timing ofreporting the results of error detection (UL subframe) in the originalUL-DL configuration before subframes other than UL subframes, DLsubframes and special subframes are added. For example, in FIG. 22, theresults of error detection in component carriers (config 0+othersubframes) in which subframes other than UL subframes, DL subframes andspecial subframes exist are reported at the same timing as that ofreporting the results of error detection of Config 0 which is theoriginal UL-DL configuration.

Although an antenna has been described in the aforementionedembodiments, the present invention may be similarly applied to anantenna port.

The term “antenna port” refers to a logical antenna including one ormore physical antennas. In other words, the term “antenna port” does notnecessarily refer to a single physical antenna, and may sometimes referto an antenna array including a plurality of antennas, and/or the like.

For example, how many physical antennas are included in the antenna portis not defined in LTE, but the antenna port is defined as the minimumunit allowing the base station to transmit different reference signalsin LTE.

In addition, an antenna port may be specified as a minimum unit to bemultiplied by a precoding vector weighting.

In the foregoing embodiments, the present invention is configured withhardware by way of example, but the invention may also be provided bysoftware in cooperation with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication ofLSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

The disclosures of Japanese Patent Application No. 2011-154890, filed onJul. 13, 2011 and Japanese Patent Application No. 2012-015257, filed onJan. 27, 2012, including the specifications, drawings and abstracts areincorporated herein by reference in their entirety.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in mobile communicationsystems or the like.

REFERENCE SIGNS LIST

-   -   100 Base station    -   200 Terminal    -   101, 208 Control section    -   102 Control information generating section    -   103, 105 Coding section    -   104, 107 Modulation section    -   106 Data transmission controlling section    -   108 Mapping section    -   109, 218 IFFT section    -   110, 219 CP adding section    -   111, 222 Radio transmitting section    -   112, 201 Radio receiving section    -   113, 202 CP removing section    -   114 PUCCH extracting section    -   115 Despreading section    -   116 Sequence control section    -   117 Correlation processing section    -   118 A/N determining section    -   119 Bundled A/N despreading section    -   120 IDFT section    -   121 Bundled A/N determining section    -   122 Retransmission control signal generating section    -   203 FFT section    -   204 Extraction section    -   205, 209 Demodulation section    -   206, 210 Decoding section    -   207 Determination section    -   211 CRC section    -   212 Response signal generating section    -   213 Coding and modulation section    -   214 Primary-spreading section    -   215 Secondary-spreading section    -   216 DFT section    -   217 Spreading section    -   220 Time multiplexing section    -   221 Selection section

1. A communication apparatus comprising: a transmitter, which, inoperation, transmits a higher layer signaling that indicates a referenceconfiguration pattern that is a reference uplink/downlink (UL/DL)configuration, which is one of a plurality of configuration patterns,each configuration pattern defining allocation of one or more uplinksubframe(s) and one or more downlink subframe(s) within a frame and, inoperation, transmits a downlink signaling for determining aconfiguration pattern for a component carrier, wherein if thetransmitted downlink signaling is received by a terminal apparatus, theconfiguration pattern for the component carrier is determined at theterminal apparatus according to the received downlink signaling, andwherein when the determined configuration pattern is different from thereference UL/DL configuration, the reference UL/DL configuration definesthe allocation of the one or more uplink subframe(s) that are inclusiveof one or more second uplink subframe(s) defined by the determinedconfiguration pattern, and the reference UL/DL configuration defines atleast one more uplink subframe than defined by the determinedconfiguration pattern; and a receiver, which, in operation, receives anuplink signal on an uplink subframe of the component carrier, the uplinksubframe being one of the one or more second uplink subframe(s) definedby the determined configuration pattern.
 2. The communication apparatusaccording to claim 1, wherein if the transmitted downlink signaling isnot received by the terminal apparatus, the reference UL/DLconfiguration is determined as the configuration pattern for thecomponent carrier at the terminal apparatus.
 3. The communicationapparatus according to claim 1, wherein the determined configurationpattern is the same as the reference UL/DL configuration.
 4. Thecommunication apparatus according to claim 1, wherein a downlinksubframe where a Cell-specific Reference Signal (CRS) measurement isallowed at the terminal apparatus is a portion of one or more seconddownlink subframe(s) that are defined by the determined configurationpattern.
 5. The communication apparatus according to claim 1, whereinthe transmitter, in operation, transmits downlink data on the componentcarrier and the receiver, in operation, receives a response signal thatindicates error detection results of the transmitted downlink data on anuplink subframe defined by the reference UL/DL configuration.
 6. Thecommunication apparatus according to claim 1, wherein the configurationpattern for the component carrier is determined according to thetransmitted downlink signaling at the terminal apparatus when theterminal apparatus is a user terminal that supports LTE Release 11, andthe reference UL/DL configuration is determined as the configurationpattern for the component carrier at the terminal apparatus when theterminal apparatus is a legacy user terminal that does not support theLTE Release
 11. 7. A communication method comprising: transmitting ahigher layer signaling that indicates a reference configuration patternthat is a reference uplink/downlink (UL/DL) configuration, which is oneof a plurality of configuration patterns, each configuration patterndefining allocation of one or more uplink subframe(s) and one or moredownlink subframe(s) within a frame and transmitting a downlinksignaling for determining a configuration pattern for a componentcarrier, wherein if the transmitted downlink signaling is received by aterminal apparatus, the configuration pattern for the component carrieris determined at the terminal apparatus according to the receiveddownlink signaling, and wherein when the determined configurationpattern is different from the reference UL/DL configuration, thereference UL/DL configuration defines the allocation of the one or moreuplink subframe(s) that are inclusive of one or more second uplinksubframe(s) defined by the determined configuration pattern, and thereference UL/DL configuration defines at least one more uplink subframethan defined by the determined configuration pattern; and receiving anuplink signal on an uplink subframe of the component carrier, the uplinksubframe being one of the one or more second uplink subframe(s) definedby the determined configuration pattern.
 8. The communication methodaccording to claim 7, wherein if the transmitted downlink signaling isnot received by the terminal apparatus, the reference UL/DLconfiguration is determined as the configuration pattern for thecomponent carrier at the terminal apparatus.
 9. The communication methodaccording to claim 7, wherein the determined configuration pattern isthe same as the reference UL/DL configuration.
 10. The communicationmethod according to claim 7, wherein a downlink subframe where aCell-specific Reference Signal (CRS) measurement is allowed at theterminal apparatus is a portion of the one or more second downlinksubframe(s) that are defined by the determined configuration pattern.11. The communication method according to claim 7, comprising:transmitting downlink data on the component carrier; and receiving aresponse signal that indicates error detection results of thetransmitted downlink data on an uplink subframe defined by the referenceUL/DL configuration.
 12. The communication method according to claim 7,wherein the configuration pattern for the component carrier isdetermined according to the transmitted downlink signaling at theterminal apparatus when the terminal apparatus is a user terminal thatsupports LTE Release 11; and the reference UL/DL configuration isdetermined as the configuration pattern for the component carrier at theterminal apparatus when the terminal apparatus is a legacy user terminalthat does not support the LTE Release 11.